Image processing device and image processing method

ABSTRACT

Provided is an image processing device that acquires a stereo image captured by a plurality of cameras each including a wide-angle lens, divides viewing angles of the cameras with reference to optical axes corrected to be parallel to each other, generates a plurality of base images in each of which a range of each divided viewing angle is reflected and a plurality of reference images on a basis of wide-angle images constituting the stereo image, applies projective transformation to the reference images, and calculates a distance to a predetermined object on a basis of corresponding image pairs of the plurality of base images and the plurality of reference images after projective transformation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase of International PatentApplication No. PCT/JP2018/022523 filed on Jun. 13, 2018, which claimspriority benefit of Japanese Patent Application No. JP 2017-125244 filedin the Japan Patent Office on Jun. 27, 2017. Each of theabove-referenced applications is hereby incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present technology relates to an image processing device, an imageprocessing method, and a program, and in particular to an imageprocessing device, an image processing method, and a program that enablemore accurate rectification of a stereo image captured by a plurality ofwide-angle cameras.

BACKGROUND ART

As a system for measuring a distance to an object that exists in athree-dimensional space, there is a stereo camera system that measuresthe distance from images captured by two (or more) cameras using thetriangulation principle (Patent Document 1).

In such a stereo camera system, in a case where the positionalrelationship between the plurality of cameras deviates from a designedvalue, the captured image is distorted and the distance cannot beaccurately measured. Therefore, a technique called rectification hasbeen developed as a technique for electronically correcting a capturedimage (Non-Patent Document 1).

By the way, with the recent progress in the semiconductor technology,the number of pixels of an image that can be captured with a digitalcamera is increasing. Therefore, a camera (hereinafter referred to as afisheye camera) equipped with a lens such as a fisheye lens that cancapture a wide range can obtain sufficient resolution, and a stereocamera system using a fisheye camera has become practical (Non-PatentDocument 2).

The conventional rectification in a stereo camera system using a fisheyecamera expands rectification in a case of using a camera with a lenswith a narrow angle of view, and is performed by projecting an image ofone fisheye camera onto one plane (Non-Patent Document 3).

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open No.    05-114099

Non-Patent Document

-   Non-Patent Document 1: “Implementation of Camera Geometry Correction    Capability in Video-Rate Stereo Machine”, Hiroshi Kano, Shigeru    Kimura, Masaya Tanaka, Takeo Kanade, Journal of The Robotics Society    of Japan, Vol. 16, No. 4, pp. 527-532, 1998-   Non-Patent Document 2: “Aurora 3D-Measurement from Whole-sky Time    Series Image Using Fish-eye Stereo Camera”, Akira Takeuchi,    Hiromitsu Fujii, Atsushi Yamashita, Masayuki Tanaka, Ryuho Kataoka,    Yoshizumi Miyoshi, Masatoshi Okutomi, Hajime Asama, Collected Works    of The Japan Society of Mechanical Engineers, Vol. 82 (2016), No.    834, pp. 15-00428-1-17, February, 2016-   Non-Patent Document 3: “3D Measurement of Objects in Water Using    Fish-eye Stereo Camera”, Tatsuya Naruse, Atsushi Yamashita, Toru    Kaneko, Yuichi Kobayashi, Journal of The Japan Society for Precision    Engineering, Vol. 79, (2013) No. 4, pp. 344-348

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In the case of projecting an image of a fisheye camera onto one plane,the projected angle of view becomes a part of a capture range of thefisheye camera, and the rectification cannot be accurately performed.

The present technology has been made in view of such a situation, andenables more accurate rectification of a stereo image captured by aplurality of wide-angle cameras.

Solutions to Problems

An image processing device according to one aspect of the presenttechnology includes an acquisition unit configured to acquire a stereoimage captured by a plurality of cameras each including a wide-anglelens; a generation unit configured to divide viewing angles of thecameras with reference to optical axes corrected to be parallel to eachother and generate a plurality of base images in each of which a rangeof each divided viewing angle is reflected and a plurality of referenceimages on the basis of wide-angle images constituting the stereo image;a projective transformation unit configured to apply projectivetransformation to the reference images; and a distance calculation unitconfigured to calculate a distance to a predetermined object on thebasis of corresponding image pairs of the plurality of base images andthe plurality of reference images after projective transformation.

A projection unit configured to project a first wide-angle image and asecond wide-angle image constituting the stereo image onto virtualspherical surfaces including the viewing angles of the cameras,respectively can be further provided. In this case, the generation unitcan be caused to reproject the first wide-angle image projected onto thevirtual spherical surface onto a plurality of planes on the virtualspherical surface to generate the plurality of base images, and toreproject the second wide-angle image projected onto the virtualspherical surface onto a plurality of planes on the virtual sphericalsurface to generate the plurality of reference images.

A correction unit configured to correct the optical axis on the basis ofthe stereo image in which a known object is reflected, and a storageunit configured to store information regarding the optical axis aftercorrection can be further provided.

A parameter generation unit configured to generate a parameter to beused for projective transformation on the basis of corresponding pointsof the base image and the reference image constituting the image paircan be further provided. In this case, the storage unit can be caused tofurther store the parameter.

The correction unit can be caused to set the optical axis aftercorrection on the basis of information stored in the storage unit, andthe projective transformation unit can be caused to perform theprojective transformation of the reference image on the basis of theparameter stored in the storage unit.

The correction unit can be caused to repeatedly perform the correctionof the optical axis until a correction error becomes equal to or lessthan a threshold.

The acquisition unit can be caused to acquire wide-angle images capturedby two of the cameras as the stereo image.

A plurality of the cameras can be further provided.

In one aspect of the present technology, the stereo image captured bythe plurality of cameras each including a wide-angle lens is acquired,and viewing angles of the cameras are divided with reference to opticalaxes corrected to be parallel to each other. Furthermore, the pluralityof base images in which ranges of divided viewing angles are reflectedand the plurality of reference images are generated on the basis of thewide-angle images constituting the stereo image, the projectivetransformation is applied to the reference images, and the distance tothe predetermined object is calculated on the basis of the image pairsof the plurality of base images and the plurality of reference imagesafter projective transformation.

Effects of the Invention

According to the present technology, rectification of a stereo imagecaptured by a plurality of wide-angle cameras can be more accuratelyperformed.

Note that effects described here are not necessarily limited, and any ofeffects described in the present disclosure may be exhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of astereo camera system according to an embodiment of the presenttechnology.

FIG. 2 is a diagram illustrating an example of a stereo image.

FIG. 3 is a diagram illustrating a principle of distance calculation.

FIG. 4 is a diagram illustrating an example of a virtual sphericalsurface set in a wide-angle image.

FIG. 5 is a diagram illustrating an example of reprojection of awide-angle image onto a plane.

FIG. 6 is a diagram illustrating an example of setting of planes.

FIG. 7 is a diagram illustrating an example of setting of a plane.

FIG. 8 is a diagram illustrating an example of a shift of an opticalaxis.

FIG. 9 is a diagram illustrating an example of optical axis correction.

FIG. 10 is a diagram illustrating an example of optical axis correction.

FIG. 11 is a diagram illustrating an example of setting of a plane.

FIG. 12 is a diagram illustrating an example of setting of a plane.

FIGS. 13A and 13B are diagrams illustrating an example of projectivetransformation.

FIG. 14 is a block diagram illustrating a configuration example of animage processing device.

FIG. 15 is a block diagram illustrating a configuration example of aparallelization processing unit.

FIG. 16 is a flowchart for describing parallelization parametergeneration processing of the image processing device.

FIG. 17 is a flowchart for describing distance calculation processing ofthe image processing device.

FIG. 18 is a flowchart for describing another parallelization parametergeneration processing of the image processing device.

FIG. 19 is a block diagram illustrating a configuration example of acomputer.

FIG. 20 is a diagram illustrating an example of a schematicconfiguration of an endoscopic surgical system.

FIG. 21 is a block diagram illustrating an example of functionalconfigurations of a camera head and a CCU illustrated in FIG. 20.

FIG. 22 is a block diagram illustrating an example of a schematicconfiguration of a vehicle control system.

FIG. 23 is an explanatory diagram illustrating an example ofinstallation positions of a vehicle exterior information detection unitand an imaging unit.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, modes for carrying out the present technology will bedescribed. Description will be given in the following order.

1. First Embodiment

2. Second Embodiment

3. Third Embodiment

4. Modification

5. Application 1

6. Application 2

1. First Embodiment

<1-1. Stereo Camera System>

FIG. 1 is a block diagram illustrating a configuration example of astereo camera system according to an embodiment of the presenttechnology.

A stereo camera system 1 illustrated in FIG. 1 is configured byconnecting a camera 12-1 and a camera 12-2 constituting a stereo camerato an image processing device 11.

The camera 12-1 and the camera 12-2 are fixed with optical axes in thesame direction in a horizontal direction or a vertical direction with apredetermined interval, and are provided with lenses having the sameviewing angle.

The camera 12-1 and the camera 12-2 capture images at the same timingand output the captured images. The image captured by the camera 12-1and the image captured by the camera 12-2 are input to the imageprocessing device 11 as a stereo image. The stereo image input to theimage processing device 11 is used to calculate a distance to an objectreflected in the stereo image.

FIG. 2 is a diagram illustrating an example of a stereo image input tothe image processing device 11.

A captured image p1 and a captured image p2 are wide-angle imagescaptured by the cameras 12-1 and 12-2 having lenses with a wide viewingangle (wide angle of view) such as a fisheye lens. Here, the wide-angleimage refers to an image having an angle of view of 120 degrees or more,particularly 150 degrees or more.

Hereinafter, description will be given on the assumption that thecameras 12-1 and 12-2 are fisheye cameras equipped with fisheye lenses.The fisheye lens is a lens having an angle of view of approximately 180degrees. The case of using two fisheye cameras will be described.However, the number of fisheye cameras used for capturing a stereo imagemay be two or more.

As illustrated in FIG. 2, the captured image p1 and the captured imagep2 are images in which a larger distortion is generated in a peripheralportion. In lower portions of the captured image p1 and the capturedimage p2, a vehicle body C of an automobile to which the cameras 12-1and 12-2 are attached is reflected in a substantially arcuate shape.

In other words, the stereo camera system 1 in FIG. 1 is, for example, anon-board system, and is used for calculating the distance to the objectduring traveling. The calculated distance is used for presenting varioustypes of information such as a warning to a driver.

<1-2. Principle of Distance Calculation>

FIG. 3 is a diagram illustrating a principle of distance calculation toan object.

In the stereo camera system 1, as illustrated in FIG. 3, imagingsurfaces of the two fisheye cameras are arranged in parallel, and thedistance to the target object is calculated using the stereo imagecaptured by these imaging surfaces. For example, an imaging surface 1illustrated on the left side in FIG. 3 is the imaging surface of thecamera 12-1, and an imaging surface 2 illustrated on the right side isthe imaging surface of the camera 12-2.

It is assumed that an object point P at a position (X, Y, Z) in athree-dimensional space is reflected at a point P1 (x1, y1) on theimaging surface 1, and is reflected at a point P2 (x2, y2) on theimaging surface 2. A distance Z to the object point P is obtained by thefollowing expression (1), where the distance between a center of theimaging surface 1 and a center of the imaging surface 2 is D and a focallength of the fisheye lenses is f.[Math. 1]Z=D·f/(x1−x2)  (1)

Since the distance D and the focal length f are fixed values determinedby the stereo camera system 1, the distance to the object point can becalculated by obtaining the values of x1 and x2. x1 and x2 are calledcorresponding points between two images, and obtaining the correspondingpoint is generally called corresponding point search. Furthermore, x1−x2in the right side denominator of the above expression (1) is the amountof deviation of the positions of the object in the images and is calledparallax.

The corresponding point search is processing of using one of twocaptured images as a base image and using the other one as a referenceimage, and searching for where in the reference image a certain point inthe base image exists. The search for the corresponding points isperformed by image processing such as block matching.

By block matching, a region most similar to the point in the base imageand a peripheral region of the point is detected from the referenceimage. Whether or not a region is similar is quantified by an evaluationexpression, and a region having the largest (or smallest) evaluationvalue is detected as the corresponding point.

As the evaluation value of the block matching, there is a sum ofdifference absolute values. A sum of difference absolute values E12 isan evaluation value based on luminance differences of the point P1 (x1,y1) and the point P2 (x2, y2) and the peripheral regions of the pointsin the two images, as expressed by the following expression (2).[Math. 2]E12=ΣmΣn|I1(x1+m,y1+n)−I2(x2+m,y2+n)|  (2)

Two regions being similar means the luminance values in the regionsbeing close. Therefore, in the case of the expression (2), it can besaid that the reliability is higher (similar) as the evaluation valueE12 is smaller, and the reliability is lower (dissimilar) as theevaluation value E12 is larger.

In the image processing device 11, for the certain point P1, processingof searching the reference image for the point P2 having the smallestvalue of the expression (2) is performed as the corresponding pointsearch. In a case where a pixel corresponding to an arbitrary pixel (apixel where the object is reflected) in the captured image p1 issearched for as the corresponding point, the distance is calculatedusing the expression (1).

In the image processing device 11, such corresponding point search anddistance calculation are mainly performed as stereo image processing.

<1-3. Rectification>

Rectification (parallelization processing) in the image processingdevice 11 will be described.

In general, a parallelization parameter, which is a parameter used forthe parallelization processing, is obtained when the two camerasconstituting the stereo camera system are fixed to a mounting jig. As amethod of obtaining the parallelization parameter, there is a methoddescribed in Document 1 below. To specify an orientation of a camera ina three-dimensional space, it is sufficient that four known points on animage are given. It is also possible to specify more points than 4points to improve the accuracy of the parallelization processing.

-   Document 1: Computer Vision—Geometry of Vision—ISBN:    978-4-339-02363-3, pp. 83-87

By the way, the cameras 12-1 and 12-2 used in the stereo camera system 1are fisheye cameras. In a case of directly projecting a captured imagecaptured by a fisheye camera onto one plane and performing theaforementioned parallelization processing, only a part of the capturedimage can be used for the processing. Therefore, the merit of taking awide range of image using the fisheye lens reduces.

FIG. 4 is a diagram illustrating an example of processing of awide-angle image captured by the camera 12-1.

A shaded wide-angle image W1 corresponds to the captured image p1captured by the camera 12-1. Since the camera 12-1 includes a range ofapproximately 180 degrees in its capture range, the wide-angle image W1can be considered to be obtained by projecting an image on a sphericalsurface of an approximately half celestial sphere onto a plane.

Therefore, in the image processing device 11, the wide-angle image W1 isprojected onto a half celestial virtual spherical surface S1. In FIG. 4,the imaging surface is on an XY plane, and the origin of thethree-dimensional space is set at the center of the imaging surface. Thecenter of the wide-angle image W1 is also located at the origin of thethree-dimensional space.

As illustrated in FIG. 4, the virtual spherical surface S1 is set tohave the same radius as the radius of the wide-angle image W1. A Z axisthat is a perpendicular to the XY plane corresponds to the optical axisof the camera 12-1, and the Z axis intersects with the virtual sphericalsurface S1 at the zenith.

Furthermore, in the image processing device 11, as illustrated in FIG.5, a projected image projected onto the virtual spherical surface S1 isreprojected onto a plurality of planes on the virtual spherical surfaceS1, and a plurality of planar images is generated.

FIG. 5 illustrates an example of projecting one wide-angle image W1 ontothe virtual spherical surface S1 and reprojecting the projected imageonto three planes. Planar images P11-1 to P13-1 are images projectedonto planes set such that centers of the respective planes are incontact with the virtual spherical surface S1.

FIG. 6 is a diagram illustrating an example of setting of planes.

FIG. 6 illustrates a state in which the virtual spherical surface andthe plurality of planes on the virtual spherical surface are viewed froma Y-axis direction. In this example, the entire viewing angle is dividedinto three viewing angles θ11 to θ13, and three planes are set in atrapezoidal shape to be projection surfaces of images in the range ofthe three viewing angles. The planes are set to be symmetric withreference to the Z axis (optical axis).

For example, the planar image P11-1 is generated by projecting a portioncorresponding to the viewing angle θ11, of the projected image obtainedby projecting the wide-angle image W1 onto the virtual spherical surfaceS1. The planar image P11-1 is an image reflecting the range of theviewing angle θ11, of the entire wide-angle image W1.

Similarly, the planar image P12-1 is generated by projecting a portioncorresponding to the viewing angle θ12, of the projected image obtainedby projecting the wide-angle image W1 onto the virtual spherical surfaceS1. The planar image P12-1 is an image reflecting the range of theviewing angle θ12, of the entire wide-angle image W1.

The planar image P13-1 is generated by projecting a portioncorresponding to the viewing angle θ13, of the projected image obtainedby projecting the wide-angle image W1 onto the virtual spherical surfaceS1. The planar image P13-1 is an image reflecting the range of theviewing angle θ13, of the entire wide-angle image W1.

The viewing angles θ11, θ12, and θ13 are set such that, for example, thesum of the viewing angles can include all viewing angles of the camera12-1. Thereby, the rectification can be performed using the entire rangecaptured in the wide-angle image captured by the fisheye camera.

Note that, here, the wide-angle image W1 is reprojected onto the threeplanes through the projection onto the virtual spherical surface S1.However, any number of planar images can be used as long as the numberis plural. The wide-angle image W1 may be directly projected onto threeplanes without to generate the plurality of planar images through theprojection onto the virtual spherical surface S1.

In the image processing device 11, as illustrated in FIG. 7, similarprocessing is applied to a wide-angle image W2 corresponding to thecaptured image p2, and planar images P11-2 to P13-2 are generatedthrough projection onto a virtual spherical surface S2.

The planar image P11-2 is an image generated by projecting a portioncorresponding to the viewing angle θ11, of a projected image obtained byprojecting the wide-angle image W2 onto the virtual spherical surfaceS2. The planar image P12-2 is an image generated by projecting a portioncorresponding to the viewing angle θ12, of a projected image obtained byprojecting the wide-angle image W2 onto the virtual spherical surfaceS2. The planar image P13-2 is an image generated by projecting a portioncorresponding to the viewing angle θ13, of a projected image obtained byprojecting the wide-angle image W2 onto the virtual spherical surfaceS2.

In the image processing device 11, the parallelization processing isperformed for each image pair of the planar image P11-1 and the planarimage P11-2, the planar image P12-1 and the planar image P12-2, and theplanar image P13-1 and the planar image P13-2, which are generated byreprojecting the images according to the same viewing angle.

Optical Axis Correction

By the way, in the case of independently performing the parallelizationprocessing for each image pair of the planar images as described above,there are some cases where an inconsistency is caused in a connectedportion of the planar images (for example, a boundary portion of theplanar image P11-1 and the planar image P12-1). A lack of distanceinformation occurs due to the inconsistency of the connected portion.

Therefore, in the image processing device 11, not to cause theinconsistency in the connected portion, optical axis correction of thetwo fisheye cameras is performed before reprojecting the projectedimages onto the plurality of planes, as described above. For example,the inconsistency in the connected portion is caused due to a deviation(nonparallel) of the optical axes of the two fisheye cameras asillustrated in FIG. 8, for example.

In the example in FIG. 8, the optical axis (solid line) of the camera12-1 used for capturing the wide-angle image W1 illustrated on the leftside deviates from the optical axis of the camera 12-2 used forcapturing the wide-angle image W2 illustrated on the right side. Forexample, by correcting the optical axis of the camera 12-1 asillustrated by the broken line, the parallelism of the optical axes ofthe two fisheye cameras is ensured.

Note that the optical axis correction in the image processing device 11is electronic processing. The processing of setting a corrected opticalaxis is performed as optical axis correction processing.

Optical axis correction in the image processing device 11 will bedescribed with reference to FIGS. 9 to 11.

FIG. 9 is a diagram illustrating an example of optical axes of thecamera 12-1 and the camera 12-2. FIG. 9 is a diagram of thethree-dimensional space of an optical system of the camera 12-1 and thecamera 12-2 described with reference to FIG. 7 and the like viewed fromthe Y-axis direction. FIGS. 10 and 11 are similarly illustrated.

In FIG. 9, as illustrated by the broken line on the left side, anoptical axis 1 of the camera 12-1 is illustrated as a perpendicular setto the center of the imaging surface 1 onto which the wide-angle imageW1 is projected. The optical axis 1 passes through the zenith of thevirtual spherical surface S1. Since the imaging surface 1 is notparallel to the XY plane, the optical axis 1 is slightly inclined withrespect to the Z axis.

Similarly, as illustrated by the broken line on the right side, anoptical axis 2 of the camera 12-2 is illustrated as a perpendicular setto the center of the imaging surface 2 onto which the wide-angle imageW2 is projected. The optical axis 2 passes through the zenith of thevirtual spherical surface S2. Since the imaging surface 2 is notparallel to the XY plane, the optical axis 2 is also slightly inclinedwith respect to the Z axis. The optical axis 1 and the optical axis 2are not parallel to each other.

After the optical axes are detected, optical axes parallel to each otherare set as corrected optical axes, as illustrated by the solid lines inFIG. 10. The corrected optical axis 1 obtained by correcting the opticalaxis 1 is an axis parallel to the Z axis set to the center of theimaging surface 1. Furthermore, the corrected optical axis 2 obtained bycorrecting the optical axis 2 is an axis parallel to the Z axis set tothe center of the imaging surface 2.

FIG. 10 illustrates only the correction in the X-axis direction.However, correction is similarly performed in the Y-axis direction andthe Z-axis direction.

Such a method of obtaining and correcting an optical axis is disclosedin, for example, Document 2 below.

-   Document 2: “Calibrating Fisheye Camera by Stripe Pattern Based upon    Spherical Model”, Masao Nakano, Shigang Li, Norishige Chiba, Journal    of The Institute of Electronics, Information and Communication    Engineers D, Vol. J90-D, No. 1, pp. 73-82 (2007)

In the method described in Document 2, a known pattern (object) iscaptured and an optical axis is obtained on the basis of a distortionFor example, the known object is arranged in an optical axis directionof the cameras with a distance sufficiently separated from the cameras.The sufficient distance referred here is only required to be a distancethat allows x1−x2 in the expression (1) to approach zero as much aspossible in the two stereo cameras.

The known object arranged in such a manner should be reflected at thezenith of each of the virtual spherical surfaces of the two stereocameras in a case where the optical axes are parallel. A position on thevirtual spherical surface at which the known object is reflected isdetected, and the optical axis is corrected by an amount correspondingto a difference between the detected position and the zenith, wherebythe corrected optical axis can be obtained.

Such optical axis correction is performed at the time of parallelizationparameter generation. The generation of the parallelization parameter isperformed at predetermined timing before the start of operation of thestereo camera system 1 (before the distance calculation is actuallyperformed). Information of the corrected optical axis is stored in theimage processing device 11 and is referred to to set the correctedoptical axis at the time of actual distance calculation.

Reprojection of the projected image projected onto the virtual sphericalsurface onto the plurality of planes as described above is performedafter setting of the corrected optical axes.

FIG. 11 is a diagram illustrating an example of projection of theprojected image.

As illustrated in FIG. 11, the plurality of planes on the virtualspherical surface is set with reference to the corrected optical axis.The viewing angle of the fisheye camera is divided with reference to thecorrected optical axis, and a plane is set according to each dividedviewing angle.

For example, the plane of the planar image P12-1 illustrated on the leftside in FIG. 11 is a plane parallel to the XY plane, in other words, aplane having the corrected optical axis 1 as a perpendicular. The planeof the planar image P11-1 and the plane of the planar image P13-1 aresimilarly set with reference to the corrected optical axis.

As illustrated in FIG. 12, the planar image P11-1 is an image generatedby projecting the range of the viewing angle θ11, of the projected imageobtained by projecting the wide-angle image W1 onto the virtualspherical surface S1.

Furthermore, the planar image P12-1 is an image generated by projectingthe range of the viewing angle θ12, of the projected image obtained byprojecting the wide-angle image W1 onto the virtual spherical surfaceS1. The planar image P13-1 is an image generated by projecting the rangeof the viewing angle θ13, of the projected image obtained by projectingthe wide-angle image W1 onto the virtual spherical surface S1.

Returning to the description of FIG. 11, the projected image obtained byprojecting the wide-angle image W2 onto the virtual spherical surface S2is also reprojected onto the planes set with reference to the correctedoptical axis 2, and the planar images P11-2 to P13-2 are generated.

Projective Transformation

In the above rectification, it can be said that the rectification iscompleted if the accuracy of various types of processing, such as thedetection accuracy of the optical axes, the accuracy of theparallelization of the two optical axes, and the projection accuracy tothe virtual spherical surfaces, are complete.

However, in reality, each accuracy has an error, and the error appearsas trapezoidal distortion on the plurality of planar images. In theimage processing device 11, correction using projective transformationis performed for each image pair of the planar images.

The projective transformation is expressed as the following expressions(3) and (4).[Math. 3]u=(x*a+y*b+c)/(x*g+y*h+1)  (3)[Math. 4]v=(x*d+y*e+f)/(x*g+y*h+1)  (4)

The variables in the expressions (3) and (4) represent the followingcontent.

x and y: X and Y coordinates before transformation

a, b, c, d, e, f, g, and h: Transformation coefficients

u and v: Coordinates after transformation

Since there are eight unknown parameters in the projectivetransformation, four corresponding points on the planes need to be knownto obtain the eight parameters.

The planar images P11-1 to P13-1 generated on the basis of thewide-angle image W1 are used as base images, and the planar images P11-2to P13-2 generated on the basis of the wide-angle image W2 are used asreference images.

Four points on the planar image P11-1 and four corresponding points onthe planar image P11-2 corresponding to the four points are specified,and simultaneous equations are solved, whereby a projectivetransformation parameter is obtained. This projective transformationparameter is a parameter for the image pair of the planar image P11-1and the planar image P11-2, and is used for projective transformation ofthe planar image P11-2 as a reference image.

Similarly, four points on the planar image P12-1 and four correspondingpoints on the planar image P12-2 corresponding to the four points arespecified, and simultaneous equations are solved, whereby a projectivetransformation parameter is obtained. This projective transformationparameter is a parameter for the image pair of the planar image P12-1and the planar image P12-2, and is used for projective transformation ofthe planar image P12-2 as a reference image.

Four points on the planar image P13-1 and four corresponding points onthe planar image P13-2 corresponding to the four points are specified,and simultaneous equations are solved, whereby a projectivetransformation parameter is obtained. This projective transformationparameter is a parameter for the image pair of the planar image P13-1and the planar image P13-2, and is used for projective transformation ofthe planar image P13-2 as a reference image.

The number of the corresponding points specified on each image may befour or more. Furthermore, as the method of specifying the correspondingpoints, an administrator may manually specify the corresponding points,or a printed known pattern such as a test chart may be used and theknown pattern may be automatically recognized by image processing. Awrong corresponding point or a low effective corresponding point may bemay excluded by the administrator from the corresponding pointsautomatically recognized by the image processing, and correspondingpoints may be so-called semi-automatically specified.

FIGS. 13A and 13B are diagrams illustrating an example of the projectivetransformation.

FIG. 13A is a diagram illustrating an example in which the planar imagesP11-1 to P13-1 as base images are expanded. It is assumed that an oblongobject O is reflected across the planar images P11-1 to P13-1.

The upper part in FIG. 13B is a diagram illustrating the expanded planarimages P11-2 to P13-2 as reference images. In this example, the object Ois distorted. Such a distortion appears due to an error in eachprocessing as described above.

In the image processing device 11, for example, projectivetransformation using the projective transformation parameter asdescribed above is applied to each of the planar images P11-2 to P13-2as reference images. By the projective transformation, the planar imagesP11-2 to P13-2 in which the object O with corrected distortion atconnected portions is reflected are obtained, as illustrated in thelower part in FIG. 13B.

Such calculation of the projective transformation parameters isperformed at the time of parallelization parameter generation. Theparallelization parameter is generated before the start of operation ofthe stereo camera system 1. Information of the projective transformationparameters is stored in the image processing device 11 and is referredto to perform the projective transformation for the reference images atthe time of actual distance calculation.

As described above, the rectification in the image processing device 11is configured by two stages of processing including the optical axiscorrection (image processing using corrected optical axes) and theprojective transformation.

Thereby, the rectification can be more accurately performed even in thecase of using a stereo camera including cameras with wide viewing anglessuch as the fisheye cameras. By accurately performing the rectification,the distance can be more accurately calculated.

<1-4. Configuration Example of Image Processing Device>

FIG. 14 is a block diagram illustrating a configuration example of theimage processing device 11.

As illustrated in FIG. 14, the image processing device 11 includes anacquisition unit 51, a parallelization processing unit 52, acorresponding point search unit 53, a parameter generation unit 54, aparallelization parameter storage unit 55, a distance calculation unit56, and a post-processing unit 57. The acquisition unit 51 includes apre-processing unit 61-1 and a pre-processing unit 61-2. At least a partof the functional units illustrated in FIG. 14 is realized by executinga predetermined program by a CPU of a computer that realizes the imageprocessing device 11.

The wide-angle images captured by the camera 12-1 and the camera 12-2are input to the acquisition unit 51. The acquisition unit 51 functionsas an acquisition unit that acquires the stereo image captured by thestereo camera.

The pre-processing unit 61-1 of the acquisition unit 51 appliespre-processing to the wide-angle image captured by the camera 12-1. Forexample, processing such as fisheye lens aberration correction isperformed as pre-processing. The pre-processing unit 61-1 outputs thewide-angle image to which the pre-processing has been applied to theparallelization processing unit 52.

Similarly, the pre-processing unit 61-2 applies pre-processing to thewide-angle image captured by the camera 12-2. The pre-processing unit61-2 outputs the wide-angle image to which the pre-processing has beenapplied to the parallelization processing unit 52.

The parallelization processing unit 52 obtains the corrected opticalaxes of the camera 12-1 and the camera 12-2 as described above at thetime of parallelization parameter generation, and stores the informationof the corrected optical axes in the parallelization parameter storageunit 55. Furthermore, the parallelization processing unit 52 outputs, tothe corresponding point search unit 53, the plurality of planar imagesgenerated by reprojecting projected images onto the plurality of planesset with reference to the corrected optical axes at the time ofparallelization parameter generation.

The parallelization processing unit 52 sets the corrected optical axeson the basis of the information of the corrected optical axes stored inthe parallelization parameter storage unit 55 at the time of actualdistance calculation, and performs reprojection onto the plurality ofplanes set with reference to the corrected optical axes to generate theplurality of planar images. Furthermore, the parallelization processingunit 52 applies the projective transformation to each of the referenceimages on the basis of the projective transformation parameter stored inthe parallelization parameter storage unit 55. The parallelizationprocessing unit 52 outputs the plurality of planar images as the baseimages and the plurality of planar images after projectivetransformation as the reference images to the corresponding point searchunit 53.

The corresponding point search unit 53 performs the corresponding pointsearch for each image pair of the planar images supplied from theparallelization processing unit 52 at the time of parallelizationparameter generation, and outputs the information of the correspondingpoints to the parameter generation unit 54. The corresponding pointsearch unit 53 performs the corresponding point search for each imagepair of the planar image P11-1 and the planar image P11-2, the planarimage P12-1 and the planar image P12-2, and the planar image P13-1 andthe planar image P13-2.

Furthermore, the corresponding point search unit 53 performs thecorresponding point search for each image pair of the planar imagessupplied from the parallelization processing unit 52 at the time ofactual distance calculation, and outputs information of thecorresponding points to the distance calculation unit 56. At the time ofactual distance calculation, the plurality of planar images as the baseimages and the plurality of planar images after projectivetransformation as the reference images are supplied from theparallelization processing unit 52. The corresponding point search unit53 performs the corresponding point search for each image pair of theplanar image P11-1 and the planar image P11-2 after projectivetransformation, the planar image P12-1 and the planar image P12-2 afterprojective transformation, and the planar image P13-1 and the planarimage P13-2 after projective transformation.

The parameter generation unit 54 generates the projective transformationparameter for each image pair on the basis of the information of thecorresponding points supplied from the corresponding point search unit53 at the time of parallelization parameter generation. The parametergeneration unit 54 outputs and stores the generated projectivetransformation parameters to the parallelization parameter storage unit55.

The parallelization parameter storage unit 55 stores the information ofthe corrected optical axes supplied from the parallelization processingunit 52 and the projective transformation parameters supplied from theparameter generation unit 54 as parallelization parameters at the timeof parallelization parameter generation. The parallelization parametersstored in the parallelization parameter storage unit 55 are read at thetime of actual distance calculation.

The distance calculation unit 56 performs the calculation of the aboveexpression (1) on the basis of the information of the correspondingpoints supplied from the corresponding point search unit 53 to calculatethe distance to the target object. The distance calculation unit 56outputs the calculated distance information to the post-processing unit57.

The post-processing unit 57 performs post-processing on the basis of thedistance information calculated by the distance calculation unit 56, andoutputs a processing result. For example, clustering and recognitionprocessing of objects using the distance information is performed as thepost-processing.

FIG. 15 is a block diagram illustrating a configuration example of theparallelization processing unit 52.

As illustrated in FIG. 15, the parallelization processing unit 52includes an optical axis detection unit 71, a virtual spherical surfaceprojection unit 72, an optical axis correction unit 73, a planeprojection unit 74, and a projective transformation unit 75.

The optical axis detection unit 71 detects the optical axis of thecamera 12-1 on the basis of the wide-angle image supplied from thepre-processing unit 61-1 and detects the optical axis of the camera 12-2on the basis of the wide-angle image supplied from the pre-processingunit 61-2. For example, the Z axis of when the wide-angle image isvirtually arranged at the origin of the XY plane is detected as theoptical axis. The optical axis detection unit 71 outputs information onthe optical axes of the cameras 12-1 and 12-2 to the virtual sphericalsurface projection unit 72.

The virtual spherical surface projection unit 72 sets the virtualspherical surface S1 to the wide-angle image W1 captured by the camera12-1, and projects the wide-angle image W1 onto the virtual sphericalsurface S1. Furthermore, the virtual spherical surface projection unit72 sets the virtual spherical surface S2 to the wide-angle image W2captured by the camera 12-2, and projects the wide-angle image W2 ontothe virtual spherical surface S2. The virtual spherical surfaces S1 andS2 are set such that the respective zeniths intersects with the opticalaxes detected by the optical axis detection unit 71. The virtualspherical surface projection unit 72 outputs the projected image of thewide-angle image W1 and the projected image of the wide-angle image W2to the optical axis correction unit 73 together with the information ofthe respective virtual spherical surfaces.

The optical axis correction unit 73 obtains the corrected optical axesof the camera 12-1 and the camera 12-2 as described above at the time ofparallelization parameter generation, and outputs and stores theinformation of the corrected optical axes to the parallelizationparameter storage unit 55. Furthermore, the optical axis correction unit73 outputs the projected image of the wide-angle image W1 and theprojected image of the wide-angle image W2 to the plane projection unit74 together with the information of the respective virtual sphericalsurfaces and the corrected optical axes.

The optical axis correction unit 73 sets the corrected optical axes onthe basis of the information of the corrected optical axes stored in theparallelization parameter storage unit 55 at the time of actual distancecalculation. The optical axis correction unit 73 outputs the projectedimage of the wide-angle image W1 and the projected image of thewide-angle image W2 to the plane projection unit 74 together with theinformation of the respective virtual spherical surfaces and thecorrected optical axes.

The plane projection unit 74 sets the plurality of planes on the virtualspherical surface S1 with reference to the corrected optical axis of thecamera 12-1, and reprojects the projected image of the wide-angle imageW1 onto the planes to generate the plurality of planar images.Furthermore, the plane projection unit 74 sets the plurality of planeson the virtual spherical surface S2 with reference to the correctedoptical axis of the camera 12-2, and reprojects the projected image ofthe wide-angle image W2 onto the planes to generate the plurality ofplanar images. The plane projection unit 74 functions as a generationunit that generates the plurality of planar images on the basis of thewide-angle images.

The plane projection unit 74 outputs the plurality of planar imagesgenerated on the basis of the wide-angle image W1 as the base images andthe plurality of planar images generated on the basis of the wide-angleimage W2 as the reference images to the corresponding point search unit53 at the time of parallelization parameter generation.

The plane projection unit 74 outputs the plurality of planar imagesgenerated on the basis of the wide-angle image W1 as the base images andthe plurality of planar images generated on the basis of the wide-angleimage W2 as the reference images to the projective transformation unit75 at the time of actual distance calculation.

Furthermore, the projective transformation unit 75 applies theprojective transformation to each of the reference images on the basisof the projective transformation parameter stored in the parallelizationparameter storage unit 55 at the time of actual distance calculation.The projective transformation unit 75 outputs the plurality of baseimages and the plurality of reference images after projectivetransformation to the corresponding point search unit 53.

<1-5. Operation of Image Processing Device>

Here, an operation of the image processing device 11 having the aboveconfiguration will be described.

First, the processing by the image processing device 11 for generatingthe parallelization parameter will be described with reference to theflowchart in FIG. 16.

The processing in FIG. 16 is performed at predetermined timing beforethe start of operation of the stereo camera system 1. The stereo imageobtained by capturing a known object prepared for generating theparallelization parameter is input to the image processing device 11.The known object used for generating the parallelization parameter maybe a three-dimensional object or may be a planar object such as a testchart on which a known pattern is printed.

In step S1, the acquisition unit 51 receives and acquires the stereoimage including the wide-angle image captured by the camera 12-1 and thewide-angle image captured by the camera 12-2.

In step S2, the pre-processing unit 61-1 applies the pre-processing tothe wide-angle image captured by the camera 12-1. Furthermore, thepre-processing unit 61-2 applies the pre-processing to the wide-angleimage captured by the camera 12-2.

In step S3, the optical axis detection unit 71 of the parallelizationprocessing unit 52 detects the optical axis of the camera 12-1 on thebasis of the wide-angle image supplied from the pre-processing unit 61-1and detects the optical axis of the camera 12-2 on the basis of thewide-angle image supplied from the pre-processing unit 61-2.

In step S4, the virtual spherical surface projection unit 72 sets thevirtual spherical surface S1 to the wide-angle image captured by thecamera 12-1, and projects the wide-angle image onto the virtualspherical surface S1. Furthermore, the virtual spherical surfaceprojection unit 72 sets the virtual spherical surface S2 to thewide-angle image captured by the camera 12-2, and projects thewide-angle image onto the virtual spherical surface S2.

In step S5, the optical axis correction unit 73 detects the position ofthe known object on the virtual spherical surface S1 by analyzing theprojected image projected onto the virtual spherical surface S1, andcorrects the optical axis by the amount corresponding to the differencebetween the position and the zenith to obtain the corrected optical axisof the camera 12-1. Furthermore, the optical axis correction unit 73detects the position of the known object on the virtual sphericalsurface S2 by analyzing the projected image projected onto the virtualspherical surface S2, and corrects the optical axis by the amountcorresponding to the difference between the position and the zenith toobtain the corrected optical axis of the camera 12-2.

In step S6, the optical axis correction unit 73 outputs and stored theinformation of the corrected optical axes of the cameras 12-1 and 12-2to the parallelization parameter storage unit 55.

In step S7, the plane projection unit 74 sets the plurality of planes onthe virtual spherical surface S1 with reference to the corrected opticalaxis of the camera 12-1, and reprojects the projected image onto theplanes to generate the plurality of base images. Furthermore, the planeprojection unit 74 sets the plurality of planes on the virtual sphericalsurface S2 with reference to the corrected optical axis of the camera12-2, and reprojects the projected image onto the planes to generate theplurality of reference images.

In step S8, the corresponding point search unit 53 performs thecorresponding point search for each image pair of the base image and thereference image supplied from the plane projection unit 74, and outputsthe information of the corresponding points to the parameter generationunit 54.

In step S9, the parameter generation unit 54 generates the projectivetransformation parameter for each image pair on the basis of thecorresponding points searched by the corresponding point search unit 53.

In step S10, the parameter generation unit 54 outputs and stores thegenerated projective transformation parameters to the parallelizationparameter storage unit 55.

Through the above processing, the parallelization parameter storage unit55 stores the information of the corrected optical axes and theprojective transformation parameters as the parallelization parameters.

Next, processing by the image processing device 11 for actuallycalculating the distance to the target object will be described withreference to the flowchart in FIG. 17.

The processing in FIG. 17 is performed at predetermined timing such asduring traveling in a state where the stereo camera system 1 is attachedto an automobile. A stereo image obtained by capturing surroundinglandscape during traveling is input to the image processing device 11.

Note that which object is targeted as an object to be calculated indistance is specified by, for example, a control unit (not illustrated)by analyzing the stereo image. Information specifying the identifiedobject is supplied to, for example, the corresponding point search unit53 and the distance calculation unit 56.

In step S31, the acquisition unit 51 receives and acquires the stereoimage including the wide-angle image captured by the camera 12-1 and thewide-angle image captured by the camera 12-2.

In step S32, the pre-processing unit 61-1 applies the pre-processing tothe wide-angle image captured by the camera 12-1. Furthermore, thepre-processing unit 61-2 applies the pre-processing to the wide-angleimage captured by the camera 12-2.

In step S33, the optical axis detection unit 71 of the parallelizationprocessing unit 52 detects the optical axis of the camera 12-1 on thebasis of the wide-angle image supplied from the pre-processing unit 61-1and detects the optical axis of the camera 12-2 on the basis of thewide-angle image supplied from the pre-processing unit 61-2.

In step S34, the virtual spherical surface projection unit 72 sets thevirtual spherical surface S1 to the wide-angle image captured by thecamera 12-1, and projects the wide-angle image onto the virtualspherical surface S1. Furthermore, the virtual spherical surfaceprojection unit 72 sets the virtual spherical surface S2 to thewide-angle image captured by the camera 12-2, and projects thewide-angle image onto the virtual spherical surface S2.

In step S35, the optical axis correction unit 73 sets the respectivecorrected optical axes of the camera 12-1 and the camera 12-2 on thebasis of the information of the corrected optical axes stored in theparallelization parameter storage unit 55.

In step S36, the plane projection unit 74 sets the plurality of planeson the virtual spherical surface S1 with reference to the correctedoptical axis of the camera 12-1, and reprojects the projected image ontothe planes to generate the plurality of base images. Furthermore, theplane projection unit 74 sets the plurality of planes on the virtualspherical surface S2 with reference to the corrected optical axis of thecamera 12-2, and reprojects the projected image onto the planes togenerate the plurality of reference images.

In step S37, the projective transformation unit 75 applies theprojective transformation to each of the reference images on the basisof the projective transformation parameter stored in the parallelizationparameter storage unit 55. The projective transformation unit 75 outputsthe plurality of base images and the plurality of reference images afterprojective transformation.

In step S38, the corresponding point search unit 53 performs thecorresponding point search for each image pair of the base image and thereference image after projective transformation supplied from theprojective transformation unit 75.

In step S39, the distance calculation unit 56 calculates the distance tothe target object on the basis of the corresponding points searched bythe corresponding point search unit 53.

In step S40, the post-processing unit 57 performs the post-processing onthe basis of the distance information calculated by the distancecalculation unit 56, and terminates the processing.

The rectification including the two-stage processing of the optical axiscorrection and the projective transformation as described above isperformed every time the distance to the target object is calculated.Thereby, the distance can be calculated with more accuracy.

2. Second Embodiment

In the optical axis correction performed as the first stage processingof the rectification as described above, the processing that may causethe largest error is the detection (estimation) of the optical axis. Ifthe detection of the optical axis has an error and the corrected opticalaxis cannot be set with high accuracy, the amount of correction in theprojective transformation performed as the second stage processingbecomes large and there is a possibility that the distortion cannot becorrected.

Here, another processing by an image processing device 11 for generatinga parallelization parameter will be described with reference to theflowchart in FIG. 18. The optical axis correction performed as the firststage processing is performed in a form different from the processingdescribed with reference to FIG. 16.

The processing in FIG. 18 is similar to the processing described withreference to FIG. 16, except that evaluation of a correction result ofoptical axes is performed. Overlapping description will be omitted asappropriate.

A stereo image obtained by capturing a known object prepared forgenerating a parallelization parameter is input to the image processingdevice 11. The known object prepared here may be a nearby object as longas the position is fixed. The known object may be an object reflectedonly in the vicinity of the zenith when projected onto a virtualspherical surface but also an object widely distributed in the entireimage.

In step S51, the stereo image is received, and in step S52,pre-processing is applied to wide-angle images constituting the stereoimage.

In step S53, an optical axis detection unit 71 of a parallelizationprocessing unit 52 detects an optical axis of a camera 12-1 and anoptical axis of a camera 12-2.

In step S54, the virtual spherical surface projection unit 72 projectsthe wide-angle image captured by the camera 12-1 and the wide-angleimage captured by the camera 12-2 onto virtual spherical surfaces.

In step S55, the optical axis correction unit 73 analyzes projectedimages and detects the positions of the known object on the virtualspherical surfaces. Furthermore, the optical axis correction unit 73corrects the optical axis by an amount corresponding to a differencebetween the detected position and a preset position (position at whichthe known object should be reflected).

In step S56, a plane projection unit 74 sets a plurality of planes onthe virtual spherical surfaces with reference to the corrected opticalaxes, and reprojects the projected images onto the planes to generate aplurality of base images and a plurality of reference images.

In step S57, the optical axis correction unit 73 determines whether ornot an optical axis correction error is equal to or less than athreshold.

The optical axis correction error is obtained by, for example, thefollowing expression (5).[Math. 5]err_sum1=Σ|y1(i)−y2(i)|  (5)

Here, y1(i) represents a y coordinate of a certain object point on thebase image. y2(i) represents a y coordinate of the same object point onthe reference image. i represents a value from 1 to n and is a serialnumber of n object points reflected in a planar image.

The fact that there is no error in the optical axis correction meansthat the same object point reflected in the two fisheye cameras has thesame value y, so the difference between the values y should be close to0. The expression (5) is an evaluation expression based on the sum ofpositional deviations of the same object point in the y directionbetween stereo cameras.

Furthermore, the optical axis correction error may be obtained by thefollowing expression (6).[Math. 6]err_sum2=Σ|x1(i)+d(i)−y2(i)|+Σ|y1(i)−y2(i)|  (6)

Here, x1(i) represents an x coordinate of a certain object point on thebase image. x2(i) represents an x coordinate of the same object point onthe reference image. y1(i), y2(i), and i are similar to the case of theexpression (5). A parallax d is a value that can be calculated using theexpression (1) from a known distance to the object point.

The expression (6) is to obtain an evaluation value including apositional deviation of the same object point in an x direction ascompared with the expression (5).

Another evaluation value may be used instead of using the error obtainedby the expressions (5) and (6) as the evaluation value. For example, thepart for obtaining the sum of errors in the expression (5) or (6) isused to obtain the sum of squares of the errors, and an evaluation valueobtained using by the expression or an evaluation value obtained byusing correlation calculation or the like may be used.

Returning to the description of FIG. 18, in a case where it isdetermined that the optical axis correction error exceeds a threshold instep S57, the processing returns to step S55 and repeats optical axiscorrection. In the optical axis correction that is repeated performed,correction according to an error may be performed, or correction forshifting the optical axis by only a fixed amount may be performed.

In a case where it is determined that the optical axis correction erroris equal to or less than the threshold in step S57, processing of stepS58 and subsequent steps is performed. By repeating the optical axiscorrection until the correction error becomes equal to or less than thethreshold, an optical axis with a small error can be obtained as thecorrected optical axes.

The processing of step S58 and subsequent steps is similar to theprocessing of step S6 and the subsequent steps in FIG. 16. With theabove processing, rectification can be performed with more accuracy.

3. Third Embodiment

Cameras 12-1 and 12-2, which are fisheye cameras, can capture a widerange. Therefore, there are some cases where a housing to which a stereocamera system 1 is attached is reflected, depending on how the stereocamera system 1 is attached.

For example, in a stereo image in FIG. 2, a vehicle body C of anautomobile is reflected as described above. In a case of projecting sucha stereo image onto a virtual spherical surface and reprojecting aprojected image onto a plurality of planes, the vehicle body C isreflected in each of planar images. Here, when the above-describedrectification is performed, the distance to the vehicle body C can becalculated.

When using the stereo camera system 1 that has completed therectification, distance measurement may not be correctly performed dueto distortion due to impact, heat, aging, or the like. In this case,such a problem is solved by performing rectification again.

However, in the rectification before the start of operation described inthe first embodiment, a dedicated environment is required because aknown pattern that covers the entire screen, for example, is used forthe optical axis correction.

Therefore, rerectification may be performed by the method described inthe second embodiment, which does not require a dedicated environment.This rerectification is performed at predetermined timing after thestart of operation of the stereo camera system 1, for example.

By evaluating an optical axis correction error using the expression (5),a deviation of rectification in a y direction can be eliminated, but adeviation in an x direction may remain. Evaluation of the optical axiscorrection error in the rerectification is performed using theexpression (6).

In the case where evaluation of the optical axis correction error isperformed using the expression (6), an object point with a knowndistance is required. For this known distance, the distance to thehousing reflected in the fisheye camera, such as the vehicle body C, canbe used.

Here, in the case of using the vehicle body C as the object point with aknown distance, the known object point is concentrated into a part of aplanar image, such as a position of a lower part of the planar image.For the object point with a known distance, an error is obtained usingthe expression (6), and for an object point with an unknown distance, anerror is obtained using the expression (5), whereby the optical axiscorrection error can be measured in the entire image.

4. Modification

The cases where the lenses included in the cameras 12-1 and 12-2 arefisheye lenses have been mainly described. However, lenses having a wideviewing angle that are not fisheye lenses may be provided in the cameras12-1 and 12-2.

Furthermore, in the above description, the reprojection of thewide-angle image projected onto the virtual spherical surface has beenperformed on the three planes set on the virtual spherical surface.However, reprojection may be performed onto four or more planes set withreference to corrected optical axes.

The image processing device 11 has been provided as a separate devicefrom the camera 12-1 and the camera 12-2 constituting the stereo camera.However, the image processing device 11 may include the camera 12-1 andthe camera 12-2, and these devices may be provided in the same housing.

The series of processing described above can be executed by hardware orsoftware. In a case where the series of processing is executed bysoftware, a program constituting the software is installed from aprogram recording medium into a computer incorporated in dedicatedhardware, a general-purpose personal computer, or the like.

FIG. 19 is a block diagram illustrating a configuration example ofhardware of a computer that executes the above-described series ofprocessing by a program. The image processing device 11 is configured bya computer having the configuration as illustrated in FIG. 19.

A central processing unit (CPU) 1001, a read only memory (ROM) 1002, anda random access memory (RAM) 1003 are mutually connected by a bus 1004.

Moreover, an input/output interface 1005 is connected to the bus 1004.An input unit 1006 including a keyboard, a mouse, and the like, and anoutput unit 1007 including a display, a speaker, and the like areconnected to the input/output interface 1005. Furthermore, a storageunit 1008 including a hard disk, a nonvolatile memory, and the like, acommunication unit 1009 including a network interface and the like, anda drive 1010 for driving a removable medium 1011 are connected to theinput/output interface 1005.

In the computer configured as described above, the CPU 1001 loads, forexample, a program stored in the storage unit 1008 into the RAM 1003 andexecutes the program via the input/output interface 1005 and the bus1004, so that the above-described series of processing is performed.

The program executed by the CPU 1001 is provided by being recorded onthe removable medium 1011 or via a wired or wireless transmission mediumsuch as a local area network, the Internet, or digital broadcasting, andis installed in the storage unit 1008.

Note that the program executed by the computer may be a programprocessed in chronological order according to the order described in thepresent specification or may be a program executed in parallel or atnecessary timing such as when a call is made.

Embodiments of the present technology are not limited to theabove-described embodiments, and various modifications can be madewithout departing from the gist of the present technology.

Note that the effects described in the present specification are merelyexamples and are not limited, and other effects may be exhibited.

5. Application 1

The technology according to the present disclosure can be applied tovarious products. For example, the technology according to the presentdisclosure may be applied to an endoscopic surgical system. The stereocamera system 1 is used as a part of the endoscopic surgical system.

FIG. 20 is a diagram illustrating an example of a schematicconfiguration of an endoscopic surgical system 5000 to which thetechnology according to the present disclosure is applicable. FIG. 20illustrates a state in which an operator (surgeon) 5067 is performingsurgery for a patient 5071 on a patient bed 5069, using the endoscopicsurgical system 5000. As illustrated, the endoscopic surgical system5000 includes an endoscope 5001, other surgical tools 5017, a supportarm device 5027 that supports the endoscope 5001, and a cart 5037 inwhich various devices for endoscopic surgery are mounted.

In endoscopic surgery, a plurality of cylindrical puncture instrumentscalled trocars 5025 a to 5025 d is punctured into an abdominal wallinstead of cutting the abdominal wall and opening the abdomen. Then, alens barrel 5003 of the endoscope 5001 and other surgical tools 5017 areinserted into a body cavity of the patient 5071 through the trocars 5025a to 5025 d. In the illustrated example, as the other surgical tools5017, a pneumoperitoneum tube 5019, an energy treatment tool 5021, and aforceps 5023 are inserted into the body cavity of the patient 5071.Furthermore, the energy treatment tool 5021 is a treatment tool forperforming incision and detachment of tissue, sealing of a blood vessel,and the like with a high-frequency current or an ultrasonic vibration.Note that the illustrated surgical tools 5017 are mere examples, andvarious kinds of surgical tools typically used in endoscopic surgerysuch as tweezers and a retractor may be used as the surgical tool 5017.

An image of an operation site in the body cavity of the patient 5071captured by the endoscope 5001 is displayed on a display device 5041.The operator 5067 performs treatment such as removal of an affectedpart, for example, using the energy treatment tool 5021 and the forceps5023 while viewing the image of the operation site displayed on thedisplay device 5041 in real time. Note that the pneumoperitoneum tube5019, the energy treatment tool 5021, and the forceps 5023 are supportedby the operator 5067, an assistant, or the like during surgery, althoughillustration is omitted.

(Support Arm Device)

The support arm device 5027 includes an arm unit 5031 extending from abase unit 5029. In the illustrated example, the arm unit 5031 includesjoint units 5033 a, 5033 b, and 5033 c, and links 5035 a and 5035 b, andis driven under the control of an arm control device 5045. The endoscope5001 is supported by the arm unit 5031, and the position and posture ofthe endoscope 5001 are controlled. With the control, stable fixation ofthe position of the endoscope 5001 can be realized.

(Endoscope)

The endoscope 5001 includes the lens barrel 5003 and a camera head 5005.A region having a predetermined length from a distal end of the lensbarrel 5003 is inserted into the body cavity of the patient 5071. Thecamera head 5005 is connected to a proximal end of the lens barrel 5003.In the illustrated example, the endoscope 5001 configured as a so-calledhard endoscope including the hard lens barrel 5003 is illustrated.However, the endoscope 5001 may be configured as a so-called softendoscope including the soft lens barrel 5003.

An opening portion in which an object lens is fit is provided in thedistal end of the lens barrel 5003. A light source device 5043 isconnected to the endoscope 5001, and light generated by the light sourcedevice 5043 is guided to the distal end of the lens barrel 5003 by alight guide extending inside the lens barrel 5003 and an observationtarget in the body cavity of the patient 5071 is irradiated with thelight through the object lens. Note that the endoscope 5001 may be aforward-viewing endoscope, an oblique-viewing endoscope, or aside-viewing endoscope.

An optical system and an imaging element are provided inside the camerahead 5005, and reflected light (observation light) from the observationtarget is condensed to the imaging element by the optical system. Theobservation light is photoelectrically converted by the imaging element,and an electrical signal corresponding to the observation light, inother words, an image signal corresponding to an observed image isgenerated. The image signal is transmitted to a camera control unit(CCU) 5039 as raw data. Note that the camera head 5005 has a function toadjust magnification and a focal length by appropriately driving theoptical system.

Note that a plurality of the imaging elements may be provided in thecamera head 5005 to support three-dimensional (3D) display, and thelike, for example. In this case, a plurality of relay optical systems isprovided inside the lens barrel 5003 to guide the observation light toeach of the plurality of imaging elements.

(Various Devices Mounted in Cart)

The CCU 5039 includes a central processing unit (CPU), a graphicsprocessing unit (GPU), and the like, and centrally controls theoperation of the endoscope 5001 and the display device 5041.Specifically, the CCU 5039 receives the image signal from the camerahead 5005, and applies various types of image processing for displayingan image based on the image signal, such as developing processing(demosaicing processing), for example, to the image signal. The CCU 5039provides the image signal to which the image processing has been appliedto the display device 5041. Furthermore, the CCU 5039 transmits acontrol signal to the camera head 5005 to control its driving. Thecontrol signal may include information regarding imaging conditions suchas the magnification and focal length.

The display device 5041 displays an image based on the image signal towhich the image processing has been applied by the CCU 5039, under thecontrol of the CCU 5039. In a case where the endoscope 5001 supportshigh-resolution capturing such as 4K (horizontal pixel number3840×vertical pixel number 2160) or 8K (horizontal pixel number7680×vertical pixel number 4320), and/or in a case where the endoscope5001 supports 3D display, for example, the display device 5041, whichcan perform high-resolution display and/or 3D display, can be usedcorresponding to each case. In a case where the endoscope 5001 supportsthe high-resolution capturing such as 4K or 8K, a greater sense ofimmersion can be obtained by use of the display device 5041 with thesize of 55 inches or more. Furthermore, a plurality of display devices5041 having different resolutions and sizes may be provided depending onthe application.

The light source device 5043 includes a light source such as a lightemitting diode (LED) for example, and supplies irradiation light to theendoscope 5001 in capturing an operation portion.

The arm control device 5045 includes a processor such as a CPU, and isoperated according to a predetermined program, thereby controlling driveof the arm unit 5031 of the support arm device 5027 according to apredetermined control method.

An input device 5047 is an input interface for the endoscopic surgicalsystem 5000. The user can input various types of information andinstructions to the endoscopic surgical system 5000 through the inputdevice 5047. For example, the user inputs various types of informationregarding surgery, such as patient's physical information andinformation of an operative procedure of the surgery, through the inputdevice 5047. Furthermore, for example, the user inputs an instruction todrive the arm unit 5031, an instruction to change the imaging conditions(such as the type of the irradiation light, the magnification, and thefocal length) of the endoscope 5001, an instruction to drive the energytreatment tool 5021, or the like through the input device 5047.

The type of the input device 5047 is not limited, and the input device5047 may be one of various known input devices. For example, a mouse, akeyboard, a touch panel, a switch, a foot switch 5057, a lever, and/orthe like can be applied to the input device 5047. In a case where atouch panel is used as the input device 5047, the touch panel may beprovided on a display surface of the display device 5041.

Alternatively, the input device 5047 is a device worn by the user, suchas a glass-type wearable device or a head mounted display (HMD), forexample, and various inputs are performed according to a gesture or aline-of-sight of the user detected by the device. Furthermore, the inputdevice 5047 includes a camera capable of detecting a movement of theuser, and various inputs are performed according to a gesture or aline-of-sight of the user detected from a video captured by the camera.Moreover, the input device 5047 includes a microphone capable ofcollecting a voice of the user, and various inputs are performed by anaudio through the microphone. In this way, the input device 5047 isconfigured to be able to input various types of information in anon-contact manner, whereby the user (for example, the operator 5067) inparticular belonging to a clean area can operate a device belonging to afilthy area in a non-contact manner. Furthermore, since the user canoperate the device without releasing his/her hand from the possessedsurgical tool, the user's convenience is improved.

A treatment tool control device 5049 controls drive of the energytreatment tool 5021 for cauterization and incision of tissue, sealing ofa blood vessel, and the like. A pneumoperitoneum device 5051 sends a gasinto the body cavity of the patient 5071 through the pneumoperitoneumtube 5019 to expand the body cavity for the purpose of securing a fieldof view by the endoscope 5001 and a work space for the operator. Arecorder 5053 is a device that can record various types of informationregarding the surgery. A printer 5055 is a device that can print thevarious types of information regarding the surgery in various formatssuch as a text, an image, or a graph.

Hereinafter, a particularly characteristic configuration in theendoscopic surgical system 5000 will be further described in detail.

(Support Arm Device)

The support arm device 5027 includes the base unit 5029 as a base andthe arm unit 5031 extending from the base unit 5029. In the illustratedexample, the arm unit 5031 includes the plurality of joint units 5033 a,5033 b, and 5033 c and the plurality of links 5035 a and 5035 bconnected by the joint unit 5033 b, but FIG. 20 illustrates theconfiguration of the arm unit 5031 in a simplified manner forsimplification. In reality, the shapes, the number, and the arrangementof the joint units 5033 a to 5033 c and the links 5035 a and 5035 b, thedirections of rotation axes of the joint units 5033 a to 5033 c, and thelike can be appropriately set so that the arm unit 5031 has a desireddegree of freedom. For example, the arm unit 5031 can be favorablyconfigured to have six degrees of freedom or more. With theconfiguration, the endoscope 5001 can be freely moved within a movablerange of the arm unit 5031. Therefore, the lens barrel 5003 of theendoscope 5001 can be inserted from a desired direction into the bodycavity of the patient 5071.

Actuators are provided in the joint units 5033 a to 5033 c, and thejoint units 5033 a to 5033 c are configured to be rotatable around apredetermined rotation axis by driving of the actuators. The driving ofthe actuators is controlled by the arm control device 5045, wherebyrotation angles of the joint units 5033 a to 5033 c are controlled anddriving of the arm unit 5031 is controlled. With the control, control ofthe position and posture of the endoscope 5001 can be realized. At thistime, the arm control device 5045 can control the drive of the arm unit5031 by various known control methods such as force control or positioncontrol.

For example, the driving of the arm unit 5031 may be appropriatelycontrolled by the arm control device 5045 according to an operationinput, and the position and posture of the endoscope 5001 may becontrolled, by an appropriate operation input by the operator 5067 viathe input device 5047 (including the foot switch 5057). With thecontrol, the endoscope 5001 at the distal end of the arm unit 5031 canbe moved from an arbitrary position to an arbitrary position, and thencan be fixedly supported at the position after the movement. Note thatthe arm unit 5031 may be operated by a so-called master-slave system. Inthis case, the arm unit 5031 can be remotely operated by the user viathe input device 5047 installed at a place distant from an operatingroom.

Furthermore, in a case where the force control is applied, the armcontrol device 5045 may perform so-called power assist control in whichthe arm control device 5045 receives an external force from the user anddrives the actuators of the joint units 5033 a to 5033 c so that the armunit 5031 is smoothly moved according to the external force. With thecontrol, the user can move the arm unit 5031 with a relatively lightforce when moving the arm unit 5031 while being in direct contact withthe arm unit 5031. Accordingly, the user can more intuitively move theendoscope 5001 with a simpler operation, and the user's convenience canbe improved.

Here, in endoscopic surgery, the endoscope 5001 has been generallysupported by a surgeon called scopist. In contrast, by use of thesupport arm device 5027, the position of the endoscope 5001 can bereliably fixed without manual operation, and thus an image of theoperation site can be stably obtained and the surgery can be smoothlyperformed.

Note that the arm control device 5045 is not necessarily provided in thecart 5037. Furthermore, the arm control device 5045 is not necessarilyone device. For example, the arm control device 5045 may be provided ineach of the joint units 5033 a to 5033 c of the arm unit 5031 of thesupport arm device 5027, and the drive control of the arm unit 5031 maybe realized by mutual cooperation of the plurality of arm controldevices 5045.

(Light Source Device)

The light source device 5043 supplies irradiation light, which is usedin capturing an operation site, to the endoscope 5001. The light sourcedevice 5043 includes, for example, an LED, a laser light source, or awhite light source configured by a combination thereof. In a case wherethe white light source is configured by a combination of RGB laser lightsources, output intensity and output timing of the respective colors(wavelengths) can be controlled with high accuracy. Therefore, whitebalance of a captured image can be adjusted in the light source device5043. Furthermore, in this case, the observation target is irradiatedwith the laser light from each of the RGB laser light sources in a timedivision manner, and the drive of the imaging element of the camera head5005 is controlled in synchronization with the irradiation timing, sothat images respectively corresponding to RGB can be captured in a timedivision manner. According to the method, a color image can be obtainedwithout providing a color filter to the imaging element.

Furthermore, drive of the light source device 5043 may be controlled tochange intensity of light to be output every predetermined time. Thedrive of the imaging element of the camera head 5005 is controlled insynchronization with change timing of the intensity of light, and imagesare acquired in a time division manner and are synthesized, whereby ahigh-dynamic range image without blocked up shadows and flaredhighlights can be generated.

Furthermore, the light source device 5043 may be configured to be ableto supply light in a predetermined wavelength band corresponding tospecial light observation. In the special light observation, forexample, so-called narrow band imaging is performed by radiating lightin a narrower band than the irradiation light (in other words, whitelight) at the time of normal observation, using wavelength dependence ofabsorption of light in a body tissue, to capture a predetermined tissuesuch as a blood vessel in a mucosal surface layer at high contrast.Alternatively, in the special light observation, fluorescenceobservation to obtain an image by fluorescence generated by radiation ofexciting light may be performed. In the fluorescence observation,irradiating the body tissue with exciting light to observe fluorescencefrom the body tissue (self-fluorescence observation), injecting areagent such as indocyanine green (ICG) into the body tissue andirradiating the body tissue with exciting light corresponding to afluorescence wavelength of the reagent to obtain a fluorescence image,or the like can be performed. The light source device 5043 can beconfigured to be able to supply narrow-band light and/or exciting lightcorresponding to such special light observation.

(Camera Head and CCU)

Functions of the camera head 5005 and the CCU 5039 of the endoscope 5001will be described in more detail with reference to FIG. 21. FIG. 21 is ablock diagram illustrating an example of functional configurations ofthe camera head 5005 and the CCU 5039 illustrated in FIG. 20.

Referring to FIG. 21, the camera head 5005 includes a lens unit 5007, animaging unit 5009, a drive unit 5011, a communication unit 5013, and acamera head control unit 5015 as its functions. Furthermore, the CCU5039 includes a communication unit 5059, an image processing unit 5061,and a control unit 5063 as its functions. The camera head 5005 and theCCU 5039 are communicatively connected with each other by a transmissioncable 5065.

First, a functional configuration of the camera head 5005 will bedescribed. The lens unit 5007 is an optical system provided in aconnection portion between the lens unit 5007 and the lens barrel 5003.Observation light taken through the distal end of the lens barrel 5003is guided to the camera head 5005 and enters the lens unit 5007. Thelens unit 5007 is configured by a combination of a plurality of lensesincluding a zoom lens and a focus lens. Optical characteristics of thelens unit 5007 are adjusted to condense the observation light on a lightreceiving surface of an imaging element of the imaging unit 5009.Furthermore, the zoom lens and the focus lens are configured to havetheir positions on the optical axis movable for adjustment of themagnification and focal point of the captured image.

The imaging unit 5009 includes an imaging element, and is disposed at arear stage of the lens unit 5007. The observation light having passedthrough the lens unit 5007 is focused on the light receiving surface ofthe imaging element, and an image signal corresponding to the observedimage is generated by photoelectric conversion. The image signalgenerated by the imaging unit 5009 is provided to the communication unit5013.

As the imaging element constituting the imaging unit 5009, for example,a complementary metal oxide semiconductor (CMOS)-type image sensorhaving Bayer arrangement and capable of color capturing is used. Notethat, as the imaging element, for example, an imaging element that cancapture a high-resolution image of 4K or more may be used. By obtainmentof the image of the operation site with high resolution, the operator5067 can grasp the state of the operation site in more detail and canmore smoothly advance the surgery.

Furthermore, the imaging element constituting the imaging unit 5009includes a pair of imaging elements for respectively obtaining imagesignals for right eye and for left eye corresponding to 3D display. Withthe 3D display, the operator 5067 can more accurately grasp the depth ofbiological tissue in the operation site. Note that, in a case where theimaging unit 5009 is configured as a multi-plate imaging unit, aplurality of systems of the lens units 5007 is provided corresponding tothe imaging elements.

Furthermore, the imaging unit 5009 may not be necessarily provided inthe camera head 5005. For example, the imaging unit 5009 may be providedimmediately after the object lens inside the lens barrel 5003.

The drive unit 5011 includes an actuator, and moves the zoom lens andthe focus lens of the lens unit 5007 by a predetermined distance alongan optical axis by the control of the camera head control unit 5015.With the movement, the magnification and focal point of the capturedimage by the imaging unit 5009 can be appropriately adjusted.

The communication unit 5013 includes a communication device fortransmitting or receiving various types of information to or from theCCU 5039. The communication unit 5013 transmits the image signalobtained from the imaging unit 5009 to the CCU 5039 through thetransmission cable 5065 as raw data. At this time, to display thecaptured image of the operation site with low latency, the image signalis favorably transmitted by optical communication. This is because, insurgery, the operator 5067 performs surgery while observing the state ofthe affected part with the captured image, and thus display of a movingimage of the operation site in as real time as possible is demanded formore safe and reliable surgery. In the case of the opticalcommunication, a photoelectric conversion module that converts anelectrical signal into an optical signal is provided in thecommunication unit 5013. The image signal is converted into the opticalsignal by the photoelectric conversion module, and is then transmittedto the CCU 5039 via the transmission cable 5065.

Furthermore, the communication unit 5013 receives a control signal forcontrolling drive of the camera head 5005 from the CCU 5039. The controlsignal includes information regarding the imaging conditions such asinformation for specifying a frame rate of the captured image,information for specifying an exposure value at the time of imaging,and/or information for specifying the magnification and the focal pointof the captured image, for example. The communication unit 5013 providesthe received control signal to the camera head control unit 5015. Notethat the control signal from that CCU 5039 may also be transmitted bythe optical communication. In this case, the communication unit 5013 isprovided with a photoelectric conversion module that converts an opticalsignal into an electrical signal, and the control signal is convertedinto an electrical signal by the photoelectric conversion module and isthen provided to the camera head control unit 5015.

Note that the imaging conditions such as the frame rate, exposure value,magnification, and focal point are automatically set by the control unit5063 of the CCU 5039 on the basis of the acquired image signal. That is,a so-called auto exposure (AE) function, an auto focus (AF) function,and an auto white balance (AWB) function are incorporated in theendoscope 5001.

The camera head control unit 5015 controls the drive of the camera head5005 on the basis of the control signal received from the CCU 5039through the communication unit 5013. For example, the camera headcontrol unit 5015 controls drive of the imaging element of the imagingunit 5009 on the basis of the information for specifying the frame rateof the captured image and/or the information for specifying exposure atthe time of imaging. Furthermore, for example, the camera head controlunit 5015 appropriately moves the zoom lens and the focus lens of thelens unit 5007 via the drive unit 5011 on the basis of the informationfor specifying the magnification and focal point of the captured image.The camera head control unit 5015 may further have a function to storeinformation for identifying the lens barrel 5003 and the camera head5005.

Note that the configuration of the lens unit 5007, the imaging unit5009, and the like is arranged in a hermetically sealed structure havinghigh airtightness and waterproofness, whereby the camera head 5005 canhave resistance to autoclave sterilization processing.

Next, a functional configuration of the CCU 5039 will be described. Thecommunication unit 5059 includes a communication device for transmittingor receiving various types of information to or from the camera head5005. The communication unit 5059 receives the image signal transmittedfrom the camera head 5005 through the transmission cable 5065. At thistime, as described above, the image signal can be favorably transmittedby the optical communication. In this case, the communication unit 5059is provided with a photoelectric conversion module that converts anoptical signal into an electrical signal, corresponding to the opticalcommunication. The communication unit 5059 provides the image signalconverted into the electrical signal to the image processing unit 5061.

Furthermore, the communication unit 5059 transmits a control signal forcontrolling drive of the camera head 5005 to the camera head 5005. Thecontrol signal may also be transmitted by the optical communication.

The image processing unit 5061 applies various types of image processingto the image signal as raw data transmitted from the camera head 5005.The image processing include various types of known signal processingsuch as development processing, high image quality processing (such asband enhancement processing, super resolution processing, noisereduction (NR) processing, and/or camera shake correction processing),and/or enlargement processing (electronic zoom processing), for example.Furthermore, the image processing unit 5061 performs wave detectionprocessing for image signals for performing AE, AF, and AWB.

The image processing unit 5061 is configured by a processor such as aCPU or a GPU, and the processor is operated according to a predeterminedprogram, whereby the above-described image processing and wave detectionprocessing can be performed. Note that in a case where the imageprocessing unit 5061 includes a plurality of GPUs, the image processingunit 5061 appropriately divides the information regarding the imagesignal and performs the image processing in parallel by the plurality ofGPUs.

The control unit 5063 performs various types of control related toimaging of the operation site by the endoscope 5001 and display of thecaptured image. For example, the control unit 5063 generates a controlsignal for controlling driving of the camera head 5005. At this time, ina case where the imaging conditions are input by the user, the controlunit 5063 generates the control signal on the basis of the input by theuser. Alternatively, in a case where the AE function, the AF function,and the AWB function are incorporated in the endoscope 5001, the controlunit 5063 appropriately calculates optimum exposure value, focal length,and white balance according to a result of the wave detection processingby the image processing unit 5061, and generates the control signal.

Furthermore, the control unit 5063 displays the image of the operationsite on the display device 5041 on the basis of the image signal towhich the image processing has been applied by the image processing unit5061. At this time, the control unit 5063 recognizes various objects inthe image of the operation site, using various image recognitiontechnologies. For example, the control unit 5063 can recognize asurgical instrument such as forceps, a specific living body portion,blood, mist at the time of use of the energy treatment tool 5021, or thelike, by detecting a shape of an edge, a color or the like of an objectincluded in the operation site image. The control unit 5063 superimposesand displays various types of surgery support information on the imageof the operation site, in displaying the image of the operation site onthe display device 5041 using the result of recognition. The surgerysupport information is superimposed, displayed, and presented to theoperator 5067, so that the surgery can be more safely and reliablyadvanced.

The transmission cable 5065 that connects the camera head 5005 and theCCU 5039 is an electrical signal cable supporting communication ofelectrical signals, an optical fiber supporting optical communication,or a composite cable thereof.

Here, in the illustrated example, the communication has been performedin a wired manner using the transmission cable 5065. However, thecommunication between the camera head 5005 and the CCU 5039 may bewirelessly performed. In a case where the communication between thecamera head 5005 and the CCU 5039 is wirelessly performed, it isunnecessary to lay the transmission cable 5065 in the operating room.Therefore, the situation in which movement of medical staffs in thesurgery room is hindered by the transmission cable 5065 can beeliminated.

The example of the endoscopic surgical system 5000 to which thetechnology according to the present disclosure is applicable has beendescribed. Note that, here, the endoscopic surgical system 5000 has beendescribed as an example. However, a system to which the technologyaccording to the present disclosure is applicable is not limited to thisexample. For example, the technology according to the present disclosuremay be applied to a flexible endoscopic system for examination or amicrosurgical system.

The technology according to the present disclosure is favorably appliedto the case where the camera provided in the camera head 5005 is astereo camera provided with a fisheye lens, and an image captured by thestereo camera is processed. By applying the technology according to thepresent disclosure, the distance to the target object point can beaccurately measured. Therefore, the surgery can be more safely and morereliably performed.

6. Application 2

Furthermore, the technology according to the present disclosure may berealized as a device mounted on any type of moving bodies including anautomobile, an electric automobile, a hybrid electric automobile, anelectric motorcycle, a bicycle, a personal mobility, an airplane, adrone, a ship, a robot, a construction machine, an agricultural machine(tractor), and the like.

FIG. 22 is a block diagram illustrating a schematic configurationexample of a vehicle control system 7000 as an example of a moving bodycontrol system to which the technology according to the presentdisclosure is applicable. A vehicle control system 7000 includes aplurality of electronic control units connected through a communicationnetwork 7010. In the example illustrated in FIG. 22, the vehicle controlsystem 7000 includes a drive system control unit 7100, a body systemcontrol unit 7200, a battery control unit 7300, a vehicle exteriorinformation detection unit 7400, a vehicle interior informationdetection unit 7500, and an integration control unit 7600. Thecommunication network 7010 that connects the plurality of control unitsmay be, for example, an on-board communication network conforming to anarbitrary standard such as a controller area network (CAN), a localinterconnect network (LIN), a local area network (LAN), or FlexRay(registered trademark).

Each control unit includes a microcomputer that performs arithmeticprocessing according to various programs, a storage unit that storesprograms executed by the microcomputer, parameters used for variouscalculations, and the like, and a drive circuit that drives variousdevices to be controlled. Each control unit includes a network I/F forcommunicating with another control unit via the communication network7010 and a communication I/F for communicating with a device, a sensor,or the like inside and outside the vehicle by wired communication orwireless communication. FIG. 22 illustrates, as functionalconfigurations of the integration control unit 7600, a microcomputer7610, a general-purpose communication I/F 7620, a dedicatedcommunication I/F 7630, a positioning unit 7640, a beacon reception unit7650, an in-vehicle device I/F 7660, an audio image output unit 7670, anon-board network I/F 7680, and a storage unit 7690. Similarly, the othercontrol units include a microcomputer, a communication I/F, a storageunit, and the like.

The drive system control unit 7100 controls operations of devicesregarding a drive system of a vehicle according to various programs. Forexample, the drive system control unit 7100 functions as a controldevice of a drive force generation device for generating drive force ofa vehicle, such as an internal combustion engine or a drive motor, adrive force transmission mechanism for transmitting drive force towheels, a steering mechanism that adjusts a steering angle of a vehicle,a braking device that generates braking force of a vehicle and the like.The drive system control unit 7100 may have a function as a controldevice of an antilock brake system (ABS), electronic stability control(ESC), or the like.

The drive system control unit 7100 is connected with a vehicle statedetection unit 7110. The vehicle state detection unit 7110 includes, forexample, at least one of a gyro sensor for detecting angular velocity ofan axial rotational motion of a vehicle body, an acceleration sensor fordetecting acceleration of the vehicle, or a sensor for detecting anoperation amount of an accelerator pedal, an operation amount of a brakepedal, a steering angle of a steering wheel, an engine speed, rotationspeed of a wheel, or the like. The drive system control unit 7100performs arithmetic processing using a signal input from the vehiclestate detection unit 7110 and controls the internal combustion engine,the drive motor, an electric power steering device, a brake device, orthe like.

The body system control unit 7200 controls operations of various devicesequipped in the vehicle body according to various programs. For example,the body system control unit 7200 functions as a control device of akeyless entry system, a smart key system, an automatic window device,and various lamps such as head lamps, back lamps, brake lamps, turnsignals, and fog lamps. In this case, radio waves transmitted from amobile device substituted for a key or signals of various switches canbe input to the body system control unit 7200. The body system controlunit 7200 receives an input of the radio waves or the signals, andcontrols a door lock device, the automatic window device, the lamps, andthe like of the vehicle.

The battery control unit 7300 controls a secondary battery 7310 that isa power supply source of the drive motor according to various programs.For example, the battery control unit 7300 receives information such asa battery temperature, a battery output voltage, or a remaining capacityof the battery from a battery device including the secondary battery7310. The battery control unit 7300 performs arithmetic processing usingthese signals to control temperature adjustment of the secondary battery7310, a cooling device provided in the battery device, or the like.

The vehicle exterior information detection unit 7400 detects informationoutside the vehicle that mounts the vehicle control system 7000. Forexample, at least one of an imaging unit 7410 or a vehicle exteriorinformation detector 7420 is connected to the vehicle exteriorinformation detection unit 7400. The imaging unit 7410 includes at leastone of a time of flight (ToF) camera, a stereo camera, a monocularcamera, an infrared camera, or another camera. The vehicle exteriorinformation detector 7420 includes, for example, at least one of anenvironmental sensor for detecting current weather or atmosphericphenomena or an ambient information detection sensor for detecting othervehicles, obstacles, pedestrians, and the like around the vehicleequipped with the vehicle control system 7000.

The environmental sensor may be, for example, at least one of a raindropsensor for detecting rainy weather, a fog sensor for detecting fog, asunshine sensor for detecting the degree of sunshine, or a snow sensorfor detecting snowfall. The ambient information detection sensor may beat least one of an ultrasonic sensor, a radar device, or a lightdetection and ranging or laser imaging detection and ranging (LIDAR)device. The imaging unit 7410 and the vehicle exterior informationdetector 7420 may be provided as independent sensors or devices,respectively, or may be provided as devices in which a plurality ofsensors or devices is integrated.

Here, FIG. 23 illustrates an example of installation positions of theimaging unit 7410 and the vehicle exterior information detector 7420.Each of imaging units 7910, 7912, 7914, 7916, and 7918 is provided on atleast one position of a front nose, side mirrors, a rear bumper, a backdoor, or an upper portion of a windshield in an interior of a vehicle7900, for example. The imaging unit 7910 provided at the front nose andthe imaging unit 7918 provided at the upper portion of the windshield inan interior of the vehicle mainly acquire front images of the vehicle7900. The imaging units 7912 and 7914 provided at the side mirrorsmainly acquire side images of the vehicle 7900. The imaging unit 7916provided at the rear bumper or the back door mainly acquires a rearimage of the vehicle 7900. The imaging unit 7918 provided at the upperportion of the windshield in the interior of the vehicle is mainly usedfor detecting a preceding vehicle, a pedestrian, an obstacle, a trafficsignal, a traffic sign, a lane, or the like.

Note that FIG. 23 illustrates an example of capture ranges of theimaging units 7910, 7912, 7914, and 7916. An imaging range a indicatesan imaging range of the imaging unit 7910 provided at the front nose,imaging ranges b and c respectively indicate imaging ranges of theimaging units 7912 and 7914 provided at the side mirrors, and an imagingrange d indicates an imaging range of the imaging unit 7916 provided atthe rear bumper or the back door. For example, a bird's-eye view imageof the vehicle 7900 as viewed from above can be obtained bysuperimposing image data imaged in the imaging units 7910, 7912, 7914,and 7916.

Vehicle exterior information detectors 7920, 7922, 7924, 7926, 7928, and7930 provided at the front, rear, side, corner, and upper portion of thewindshield in the interior of the vehicle 7900 may be ultrasonic sensorsor radar devices, for example. Vehicle exterior information detectors7920, 7926, and 7930 provided at the front nose, the rear bumper, theback door, and the upper portion of the windshield in the interior ofthe vehicle 7900 may be LIDAR devices, for example. These vehicleexterior information detectors 7920 to 7930 are mainly used fordetecting a preceding vehicle, a pedestrian, an obstacle, and the like.

Referring back to FIG. 22, the description will be continued. Thevehicle exterior information detection unit 7400 causes the imaging unit7410 to image an image outside the vehicle, and receives the imagedimage. Furthermore, the vehicle exterior information detection unit 7400receives detection information from the connected vehicle exteriorinformation detector 7420. In a case where the vehicle exteriorinformation detector 7420 is an ultrasonic sensor, a radar device, or anLIDAR device, the vehicle exterior information detection unit 7400transmits ultrasonic waves, electromagnetic waves, or the like andreceives information of received reflected waves. The vehicle exteriorinformation detection unit 7400 may perform object detection processingor distance detection processing of persons, vehicles, obstacles, signs,letters or the like on a road surface on the basis of the receivedimage. The vehicle exterior information detection unit 7400 may performenvironment recognition processing of recognizing rainfall, fog, a roadsurface condition, or the like on the basis of the received information.The vehicle exterior information detection unit 7400 may calculate thedistance to the object outside the vehicle on the basis of the receivedinformation.

Furthermore, the vehicle exterior information detection unit 7400 mayperform image recognition processing or distance detection processing ofrecognizing persons, vehicles, obstacles, signs, letters, or the like ona road surface on the basis of the received image data. The vehicleexterior information detection unit 7400 may perform processing such asdistortion correction or alignment for the received image data andcombine the image data imaged by different imaging units 7410 togenerate a bird's-eye view image or a panoramic image. The vehicleexterior information detection unit 7400 may perform viewpointconversion processing using the image data imaged by the differentimaging units 7410.

The vehicle interior information detection unit 7500 detects informationinside the vehicle. A driver state detection unit 7510 that detects astate of a driver is connected to the vehicle interior informationdetection unit 7500, for example. The driver state detection unit 7510may include a camera for imaging the driver, a biometric sensor fordetecting biological information of the driver, a microphone forcollecting sounds in the interior of the vehicle, and the like. Thebiometric sensor is provided, for example, on a seating surface, asteering wheel, or the like, and detects the biological information ofan occupant sitting on a seat or the driver holding the steering wheel.The vehicle interior information detection unit 7500 may calculate thedegree of fatigue or the degree of concentration of the driver or maydetermine whether or not the driver falls asleep at the wheel on thebasis of detection information input from the driver state detectionunit 7510. The vehicle interior information detection unit 7500 mayperform processing such as noise canceling processing for collectedsound signals.

The integration control unit 7600 controls the overall operation in thevehicle control system 7000 according to various programs. Theintegration control unit 7600 is connected with an input unit 7800. Theinput unit 7800 is realized by, a device that can be operated and inputby an occupant, such as a touch panel, a button, a microphone, a switch,or a lever, for example. Data obtained by recognizing sounds input bythe microphone may be input to the integration control unit 7600. Theinput unit 7800 may be, for example, a remote control device using aninfrared ray or another radio wave, or may be an externally connecteddevice such as a mobile phone or a personal digital assistant (PDA)corresponding to the operation of the vehicle control system 7000. Theinput unit 7800 may be, for example, a camera, and in this case, theoccupant can input information by gesture. Alternatively, data obtainedby detecting movement of a wearable device worn by the occupant may beinput. Moreover, the input unit 7800 may include, for example, an inputcontrol circuit that generates an input signal on the basis of theinformation input by the occupant or the like using the above input unit7800 and outputs the input signal to the integration control unit 7600,and the like. The occupant or the like inputs various data to andinstructs the vehicle control system 7000 on a processing operation byoperating the input unit 7800.

The storage unit 7690 may include a read only memory (ROM) for storingvarious programs executed by the microcomputer, and a random accessmemory (RAM) for storing various parameters, calculation results, sensorvalues, or the like. Furthermore, the storage unit 7690 may be realizedby a magnetic storage device such as a hard disc drive (HDD), asemiconductor storage device, an optical storage device, amagneto-optical storage device, or the like.

The general-purpose communication I/F 7620 is a general-purposecommunication I/F that mediates communication with various devicesexisting in an external environment 7750. The general-purposecommunication I/F 7620 may include a cellular communication protocolsuch as global system of mobile communications (GSM) (registeredtrademark), WiMAX (registered trademark), long term evolution (LTE)(registered trademark), or LTE-advanced (LTE-A), or a wirelesscommunication protocol such as a wireless LAN (also referred to as Wi-Fi(registered trademark)) or Bluetooth (registered trademark). Thegeneral-purpose communication I/F 7620 may be connected to a device (forexample, an application server or a control server) existing on anexternal network (for example, the Internet, a cloud network, or acompany specific network) via a base station or an access point, forexample. Furthermore, the general-purpose communication I/F 7620 may beconnected with a terminal (for example, a terminal of a driver, apedestrian or a shop, or a machine type communication (MTC) terminal)existing in the vicinity of the vehicle, using a peer to peer (P2P)technology, for example.

The dedicated communication I/F 7630 is a communication I/F supporting acommunication protocol formulated for use in the vehicle. For example,the dedicated communication I/F 7630 may include a standard protocolsuch as a wireless access in vehicle environment (WAVE), which is acombination of a lower layer IEEE 802.11p and an upper layer IEEE 1609,dedicated short range communications (DSRC), or a cellular communicationprotocol. The dedicated communication I/F 7630 typically performs V2Xcommunication that is a concept including one or more of vehicle tovehicle communication, vehicle to infrastructure communication, vehicleto home communication, and vehicle to pedestrian communication.

The positioning unit 7640 receives a global navigation satellite system(GNSS) signal from a GNSS satellite (for example, a global positioningsystem (GPS) signal from a GPS satellite) to execute positioning, andgenerates position information including the latitude, longitude, andaltitude of the vehicle, for example. Note that the positioning unit7640 may specify a current position by exchanging signals with awireless access point or may acquire the position information from aterminal such as a mobile phone, a PHS, or a smartphone having apositioning function.

The beacon reception unit 7650 receives, for example, a radio wave or anelectromagnetic wave transmitted from a wireless station or the likeinstalled on a road, and acquires information such as a currentposition, congestion, road closure, or required time. Note that thefunction of the beacon reception unit 7650 may be included in theabove-described dedicated communication I/F 7630.

The in-vehicle device I/F 7660 is a communication interface thatmediates connection between the microcomputer 7610 and variousin-vehicle devices 7760 existing in the vehicle. The in-vehicle deviceI/F 7660 may establish wireless connection using a wirelesscommunication protocol such as a wireless LAN, Bluetooth (registeredtrademark), near field communication (NFC), or wireless USB (WUSB).Furthermore, the in-vehicle device I/F 7660 may establish wiredconnection such as a universal serial bus (USB), a high-definitionmultimedia interface (HDMI) (registered trademark), mobilehigh-definition link (MHL), or the like via a connection terminal (notillustrated) (and a cable if necessary). The in-vehicle device 7760 mayinclude, for example, at least one of a mobile device or a wearabledevice possessed by an occupant or an information device carried in orattached to the vehicle. Furthermore, the in-vehicle device 7760 mayinclude a navigation device that performs a route search to an arbitrarydestination. The in-vehicle device I/F 7660 exchanges control signals ordata signals with these in-vehicle devices 7760.

The on-board network I/F 7680 is an interface that mediatescommunication between the microcomputer 7610 and the communicationnetwork 7010. The on-board network I/F 7680 transmits and receivessignals and the like according to a predetermined protocol supported bythe communication network 7010.

The microcomputer 7610 of the integration control unit 7600 controls thevehicle control system 7000 according to various programs on the basisof information acquired via at least one of the general-purposecommunication I/F 7620, the dedicated communication I/F 7630, thepositioning unit 7640, the beacon reception unit 7650, the in-vehicledevice I/F 7660, or the on-board network I/F 7680. For example, themicrocomputer 7610 may calculate a control target value of the driveforce generation device, the steering mechanism, or the brake device onthe basis of the acquired information of the interior and the exteriorof the vehicle, and output a control command to the drive system controlunit 7100. For example, the microcomputer 7610 may perform cooperativecontrol for the purpose of realization of an advanced driver assistancesystem (ADAS) function including collision avoidance or shock mitigationof the vehicle, following travel based on an inter-vehicle distance,vehicle speed maintaining travel, collision warning of the vehicle, laneout warning of the vehicle and the like. Furthermore, the microcomputer7610 may control the drive force generation device, the steeringmechanism, the braking device, or the like on the basis of the acquiredinformation of a vicinity of the vehicle to perform cooperative controlfor the purpose of automatic driving of autonomous travel withoutdepending on an operation of the driver or the like.

The microcomputer 7610 may create three-dimensional distance informationbetween the vehicle and an object such as a peripheral structure orperson and may create local map information including peripheralinformation of the current position of the vehicle on the basis ofinformation acquired via at least one of the general-purposecommunication I/F 7620, the dedicated communication I/F 7630, thepositioning unit 7640, the beacon reception unit 7650, the in-vehicledevice I/F 7660, or the on-board network I/F 7680. Furthermore, themicrocomputer 7610 may predict danger such as a collision of thevehicle, approach of a pedestrian or the like, or entry of thepedestrian or the like into a closed road on the basis of the acquiredinformation, and generate a warning signal. The warning signal may be,for example, a signal for generating a warning sound or for lighting awarning lamp.

The audio image output unit 7670 transmits an output signal of at leastone of an audio or an image to an output device that can visually andaurally notify information to the occupant of the vehicle or outside thevehicle of information. In the example in FIG. 22, as the output device,an audio speaker 7710, a display unit 7720, and an instrument panel 7730are exemplarily illustrated. The display unit 7720 may include, forexample, at least one of an on-board display or a head-up display. Thedisplay unit 7720 may have an augmented reality (AR) display function.The output device may be a wearable device such as a headphone or aspectacular display worn by an occupant, a projector, a lamp, or thelike other than the aforementioned devices. In the case where the outputdevice is a display device, the display device visually displays aresult obtained in various types of processing performed by themicrocomputer 7610 or information received from another control unit, invarious formats such as a text, an image, a table, and a graph.Furthermore, in the case where the output device is an audio outputdevice, the audio output device converts an audio signal includingreproduced audio data, acoustic data, or the like into an analog signal,and aurally outputs the analog signal.

Note that, in the example illustrated in FIG. 22, at least two controlunits connected via the communication network 7010 may be integrated asone control unit. Alternatively, an individual control unit may beconfigured by a plurality of control units. Moreover, the vehiclecontrol system 7000 may include another control unit (not illustrated).Furthermore, in the above description, some or all of the functionscarried out by any one of the control units may be performed by anothercontrol unit. That is, predetermined arithmetic processing may beperformed by any of the control units as long as information istransmitted and received via the communication network 7010. Similarly,a sensor or a device connected to any of the control units may beconnected to another control unit, and a plurality of control units maytransmit and receive detection information to each other via thecommunication network 7010.

Note that a computer program for realizing the functions of the imageprocessing device 11 according to the present embodiment described withreference to FIGS. 14 and 15 can be mounted in any of the control unitsor the like. Furthermore, a computer-readable recording medium in whichsuch a computer program is stored can be provided. The recording mediumis, for example, a magnetic disk, an optical disk, a magneto-opticaldisk, a flash memory, or the like. Furthermore, the above computerprogram may be delivered via, for example, a network without using arecording medium.

In the above-described vehicle control system 7000, the image processingdevice 11 can be applied to the integration control unit 7600 of theapplication example illustrated in FIG. 22. For example, eachconfiguration of the image processing device in FIGS. 14 and 15 can berealized in the integration control unit 7600.

Furthermore, at least part of the configuration elements of the imageprocessing device 11 described with reference to FIGS. 14 and 15 may berealized in a module (for example, an integrated circuit moduleconfigured by one die) for the integration control unit 7600 illustratedin FIG. 22. Alternatively, the image processing device 11 described withreference to FIGS. 14 and 15 may be realized by a plurality of thecontrol units of the vehicle control system 7000 illustrated in FIG. 22.

[Combination Examples of Configurations]

The present technology may have the following configurations.

(1)

An image processing device including:

an acquisition unit configured to acquire a stereo image captured by aplurality of cameras each including a wide-angle lens;

a generation unit configured to divide viewing angles of the cameraswith reference to optical axes corrected to be parallel to each otherand generate a plurality of base images in each of which a range of eachdivided viewing angle is reflected and a plurality of reference imageson the basis of wide-angle images constituting the stereo image;

a projective transformation unit configured to apply projectivetransformation to the reference images; and

a distance calculation unit configured to calculate a distance to apredetermined object on the basis of corresponding image pairs of theplurality of base images and the plurality of reference images afterprojective transformation.

(2)

The image processing device according to (1), further including:

a projection unit configured to project a first wide-angle image and asecond wide-angle image constituting the stereo image onto virtualspherical surfaces including the viewing angles of the cameras,respectively, in which

the generation unit

reprojects the first wide-angle image projected onto the virtualspherical surface onto a plurality of planes on the virtual sphericalsurface to generate the plurality of base images, and

reprojects the second wide-angle image projected onto the virtualspherical surface onto a plurality of planes on the virtual sphericalsurface to generate the plurality of reference images.

(3)

The image processing device according to (1) or (2), further including:

a correction unit configured to correct the optical axis on the basis ofthe stereo image in which a known object is reflected; and

a storage unit configured to store information regarding the opticalaxis after correction.

(4)

The image processing device according to (3), further including:

a parameter generation unit configured to generate a parameter to beused for projective transformation on the basis of corresponding pointsof the base image and the reference image constituting the image pair,in which

the storage unit further stores the parameter.

(5)

The image processing device according to (4), in which

the correction unit sets the optical axis after correction on the basisof information stored in the storage unit, and

the projective transformation unit performs the projectivetransformation of the reference image on the basis of the parameterstored in the storage unit.

(6)

The image processing device according to any one of (3) to (5), in which

the correction unit repeatedly performs the correction of the opticalaxis until a correction error becomes equal to or less than a threshold.

(7)

The image processing device according to any one of (1) to (6), in which

the acquisition unit acquires wide-angle images captured by two of thecameras as the stereo image.

(8)

The image processing device according to any one of (1) to (7), furtherincluding:

the plurality of cameras.

(9)

An image processing method including the steps of:

acquiring a stereo image captured by a plurality of cameras eachincluding a wide-angle lens;

dividing viewing angles of the cameras with reference to optical axescorrected to be parallel to each other;

generating a plurality of base images in each of which a range of eachdivided viewing angle is reflected and a plurality of reference imageson the basis of wide-angle images constituting the stereo image;

applying projective transformation to the reference images; and

calculating a distance to a predetermined object on the basis ofcorresponding image pairs of the plurality of base images and theplurality of reference images after projective transformation.

(10)

A program for causing a computer to execute processing including thesteps of:

acquiring a stereo image captured by a plurality of cameras eachincluding a wide-angle lens;

dividing viewing angles of the cameras with reference to optical axescorrected to be parallel to each other;

generating a plurality of base images in each of which a range of eachdivided viewing angle is reflected and a plurality of reference imageson a basis of wide-angle images constituting the stereo image;

applying projective transformation to the reference images; and

calculating a distance to a predetermined object on a basis ofcorresponding image pairs of the plurality of base images and theplurality of reference images after projective transformation.

REFERENCE SIGNS LIST

-   1 Stereo camera system-   11 Image processing device-   12-1, 12-2 Camera-   51 Acquisition unit-   52 Parallelization processing unit-   53 Corresponding point search unit-   54 Parameter generation unit-   55 Parallelization parameter storage unit-   56 Distance calculation unit-   57 Post-processing unit-   61-1, 61-2 Pre-processing unit-   71 Optical axis detection unit-   72 Virtual spherical surface projection unit-   73 Optical axis correction unit-   74 Plane projection unit-   75 Projective transformation unit

The invention claimed is:
 1. An image processing device, comprising: anacquisition unit configured to acquire a stereo image captured by aplurality of cameras, wherein each camera of the plurality of camerasincludes a wide-angle lens, and the stereo image includes a firstwide-angle image captured by a first camera of the plurality of camerasand a second wide-angle image captured by a second camera of theplurality of cameras; a projection unit configured to project the firstwide-angle image onto a first virtual spherical surface and the secondwide-angle image onto a second virtual spherical surface; a correctionunit configured to correct, based on the stereo image, an optical axisof the first camera and an optical axis of the second camera, whereinthe corrected optical axis of the first camera is parallel to thecorrected optical axis of the second camera; a generation unitconfigured to: divide viewing angles of the plurality of cameras withreference to the corrected optical axis of the first camera and thecorrected optical axis of the second camera; reproject the projectedfirst wide-angle image onto a first plurality of planes that is on thefirst virtual spherical surface; reproject the projected secondwide-angle image onto a second plurality of planes that is on the secondvirtual spherical surface; generate a plurality of base images based onthe reprojection of the projected first wide-angle image onto the firstplurality of planes; and generate a plurality of reference images basedon the reprojection of the projected second wide-angle image onto thesecond plurality of planes, wherein each base image of the plurality ofbase images reflects a range of a corresponding viewing angle of thedivided viewing angles; a projective transformation unit configured toapply projective transformation to each reference image of the pluralityof reference images; and a distance calculation unit configured tocalculate, after the projective transformation, a distance to a firstobject based on corresponding image pairs of the plurality of baseimages and the plurality of reference images.
 2. The image processingdevice according to claim 1, wherein the first wide-angle image and thesecond wide-angle image include the viewing angles of the plurality ofcameras.
 3. The image processing device according to claim 1, furthercomprising a storage unit configured to store information regarding thecorrected optical axis of the first camera and the corrected opticalaxis of the second camera, wherein the stereo image includes a secondobject.
 4. The image processing device according to claim 3, furthercomprising a parameter generation unit configured to generate aparameter for the projective transformation, based on correspondingpoints of a base image of the plurality of base images and acorresponding reference image of the plurality of reference images,wherein the base image and the corresponding reference image constitutean image pair of the corresponding image pairs, and the storage unit isfurther configured to store the parameter for the projectivetransformation.
 5. The image processing device according to claim 4,wherein the correction unit is further configured to set the correctedoptical axis of the first camera and the corrected optical axis of thesecond camera, based on the stored information regarding the correctedoptical axis of the first camera and the corrected optical axis of thesecond camera, and the projective transformation unit is furtherconfigured to apply the projective transformation to each referenceimage of the plurality of reference images based on the storedparameter.
 6. The image processing device according to claim 3, whereinthe correction unit is further configured to repeatedly correct theoptical axis of the first camera and the optical axis of the secondcamera until a correction error becomes equal to or less than athreshold value.
 7. The image processing device according to claim 1,further comprising the plurality of cameras.
 8. An image processingmethod, comprising: acquiring a stereo image captured by a plurality ofcameras, wherein each camera of the plurality of cameras includes awide-angle lens, and the stereo image includes a first wide-angle imagecaptured by a first camera of the plurality of cameras and a secondwide-angle image captured by a second camera of the plurality ofcameras; projecting the first wide-angle image onto a first virtualspherical surface and the second wide-angle image onto a second virtualspherical surface; correcting, based on the stereo image, an opticalaxis of the first camera and an optical axis of the second camera,wherein the corrected optical axis of the first camera is parallel tothe corrected optical axis of the second camera; dividing viewing anglesof the plurality of cameras with reference to the corrected optical axisof the first camera and the corrected optical axis of the second camera;reprojecting the projected first wide-angle image onto a first pluralityof planes that is on the first virtual spherical surface; reprojectingthe projected second wide-angle image onto a second plurality of planesthat is on the second virtual spherical surface; generating a pluralityof base images based on the reprojection of the projected firstwide-angle image onto the first plurality of planes; and generating aplurality of reference images based on the reprojection of the projectedsecond wide-angle image onto the second plurality of planes, whereineach base image of the plurality of base images reflects a range of acorresponding viewing angle of the divided viewing angles; applyingprojective transformation to each reference image of the plurality ofreference images; and calculating, after the projective transformation,a distance to a specific object based on corresponding image pairs ofthe plurality of base images and the plurality of reference images.
 9. Anon-transitory computer-readable medium having stored thereoncomputer-executable instructions which, when executed by a processor,cause the processor to execute operations, the operations comprising:acquiring a stereo image captured by a plurality of cameras, whereineach camera of the plurality of cameras includes a wide-angle lens, andthe stereo image includes a first wide-angle image captured by a firstcamera of the plurality of cameras and a second wide-angle imagecaptured by a second camera of the plurality of cameras; projecting thefirst wide-angle image onto a first virtual spherical surface and thesecond wide-angle image onto a second virtual spherical surface;correcting, based on the stereo image, an optical axis of the firstcamera and an optical axis of the second camera, wherein the correctedoptical axis of the first camera is parallel to the corrected opticalaxis of the second camera; dividing viewing angles of the plurality ofcameras with reference to the corrected optical axis of the first cameraand the corrected optical axis of the second camera; reprojecting theprojected first wide-angle image onto a first plurality of planes thatis on the first virtual spherical surface; reprojecting the projectedsecond wide-angle image onto a second plurality of planes that is on thesecond virtual spherical surface; generating a plurality of base imagesbased on the reprojection of the projected first wide-angle image ontothe first plurality of planes; and generating a plurality of referenceimages based on the reprojection of the projected second wide-angleimage onto the second plurality of planes, wherein each base image ofthe plurality of base images reflects a range of a corresponding viewingangle of the divided viewing angles; applying projective transformationto each reference image of the plurality of reference images; andcalculating, after the projective transformation, a distance to aspecific object based on corresponding image pairs of the plurality ofbase images and the plurality of reference images.